The vocabulary of CET-4 is relatively simple, with a small amount. The general vocabulary is around 4000, including 3500 words necessary for high school. The rest of the words are not very difficult. As long as you have a little memory, the preparation time for Band 4 is also sufficient. To the next level, the difficulty of level 6 is higher than that of level 4. The general vocabulary is about 5500, and the probability of difficult words in reading and listening is high, so you still need to recite them carefully.
In my opinion, vocabulary will still affect your reading and writing speed in CET-4 and CET-6, and it will also affect the effect of listening. You still have to remember it carefully. Let me recommend some of my methods.
There must be a vocabulary book for CET-4 and CET-6. I usually recite twenty or thirty words a day. I must recite them from the beginning until I know them thoroughly. Usually, we can remember them in context. Of course, you can also use them to make sentences, which can strengthen your memory. In addition, review is also very important. Don't forget the day before by reciting one day. Do more exercises to consolidate it.