There is no requirement for CET-4 for postgraduate entrance examination. However, if you want to go to graduate school, you must at least graduate. Generally, you have to pass CET-4 to get a degree certificate, so it still depends on what the school requires you to issue a degree certificate. The biggest difference between English for postgraduate entrance examination and CET-4 is that there is no listening. Everything else is just an exam in China. Nothing, it's not difficult to cross the line.