In English listening teaching, the usual method is for teachers to explain vocabulary and background knowledge to students in advance. In the early research of listening teaching, many teachers thought that vocabulary and background knowledge were two important factors affecting listening comprehension, but they were basically limited to experience and there was no systematic and scientific empirical research. In recent ten years, some researchers have done some empirical research on the influence of background knowledge on listening comprehension and achieved some results, but the following three aspects are still worthy of further study and discussion: First, whether background knowledge will have different effects on listeners with different listening levels and how to explain them theoretically. Second, the actual effect of the teaching method of background knowledge input before listening. Thirdly, the relative importance of background knowledge and vocabulary to listening comprehension. This study discusses the relative influence of vocabulary and background knowledge on listeners with different listening levels through empirical methods, and tests and compares the actual effects of two teaching methods: vocabulary input before listening and background knowledge input. * * * Two experiments were designed. Sixty-eight subjects came from the first year of English major in National University of Defense Technology and were in two natural classes. The two classes were set as experimental group and control group respectively. All subjects took a vocabulary test (experiment 1 only) and a listening comprehension test. The test results will constitute the experimental data of this study. All the subjects used one or two corpora, and their topics were familiar and unfamiliar, respectively, to test the following hypotheses: the subjects' comprehension test scores on the familiar corpora were higher than those on the unfamiliar corpora; There is a significant positive correlation between the scores of pre-listening vocabulary test and post-listening comprehension test. In experiment 2, two unfamiliar corpora were used, and only the experimental group accepted the input of vocabulary and background knowledge before listening to test the following hypotheses: under the premise of having relevant background and vocabulary knowledge before listening, the subjects in the experimental group scored higher in the comprehension test than the control group; When the subjects in the experimental group had relevant vocabulary knowledge before listening, they scored higher in the comprehension test than when they had relevant background knowledge before listening. In this study, the correlation test and independent sample T test in statistics were used to statistically analyze the subjects' vocabulary test scores and comprehension test scores. The results of statistical analysis show that vocabulary knowledge has an important influence on listening comprehension, regardless of the listening level of the subjects. Similar to some previous research results, the background knowledge of the subjects also has an impact on their listening comprehension, but its significant impact is only reflected in the subjects with higher listening level. The results also show that vocabulary input before listening is more effective and easier to implement than background knowledge input in actual listening teaching. The author uses the listening comprehension process theory and schema theory to explain the above research results, and thinks that it is necessary to use relevant background knowledge to predict and reason the captured information in the listening comprehension process, and to use vocabulary knowledge to test and confirm the previous prediction and reasoning. The subjects with higher listening level have a solid vocabulary foundation, so they can more accurately test the predictions and inferences made in listening comprehension, thus proving the role and influence of vocabulary and background knowledge in listening comprehension. At the same time, if the existing schema structure in the listener's mind lacks the necessary vocabulary and related background knowledge, it will affect the rapid and accurate formation of meaning. Based on the conclusion of the study, the author puts forward some suggestions to improve listening teaching and some concrete methods to effectively implement pre-listening activities.