You think you have made many grammatical mistakes, because your English grammar is not good. The problem in this respect is that grammar must be mastered: 1, ten parts of speech, the usage characteristics of each part of speech and its syntactic function and position in the sentence. 2. Verb tenses, the usage characteristics of sixteen tenses, their sentence structures and adverbials of time used together must be clear and easy to use. 3. Verb voice, make clear the active voice and passive voice of verbs, and when to use passive voice is more appropriate. 4. The mood of verbs, whether a sentence is declarative mood, interrogative mood, imperative mood mood or subjunctive mood, should be properly positioned according to the needs of expression. 5. Usage of non-predicate verbs, correct memory and application of fixed phrases and fixed collocation. 6. Subject and predicate are consistent. 7. Correct use of simple sentences, complex sentences and complex sentences, and correct analysis of sentence components. Therefore, it is necessary to know where your mistakes are, so that you can correct them correctly. Even if you don't make mistakes again, you should pay attention to the differences between Chinese and Western cultural expressions. In addition, for how to polish the English of the thesis, my suggestion is to pay attention to the correct use of adjectives, adverbs and other modifiers and related words, as well as the use of long sentences, that is, complex sentences and advanced sentences. If you blindly use simple sentences, even if there are no mistakes in the article, it will not improve much. On the contrary, it will make the article look stiff, pale and weak, and even fail to get high marks. Therefore, when writing, we should polish it in time according to the situation and express it appropriately and correctly as needed.