A method of compositing video signals includes: obtaining at least two video signals to be composited; determining a multiplier point mode corresponding to each of the at least two video signals; performing a byte size adjustment on the at least two video signals respectively according to the multiplier point mode corresponding to each of the at least two video signals; performing a composite modulation on bytes corresponding to the at least two video signals after the byte size adjustment, and outputting composite-modulated data through a target signal interface of an analog-to-digital conversion chip.