Will watching movies online on mobile phones consume a lot of traffic?

It depends on what software you use and the size and quality of the video. Looking at the Q screen with uc is about J500-700kb/min, and it took nearly 100 megabytes in two or three hours. What should I do after I spend it? A month is a long time. I suggest you just watch short videos on your mobile phone, not movies, unless you use an unlimited card.