A screen coding method and system based on mass center coincidence. The screen coding method based on mass center coincidence includes: constructing a plurality of coding unit models composed of a combination of a plurality of geometric figures with coincident mass centers, where vertices of the geometric figures do not coincide; and filling in data information to each vertex of the coding unit models according to a method of data information arrangement of a plurality of data combinations to generate a coding unit so as to implement different data lengths of the same coding unit. As such, a data length of the coding unit can be controlled, so that when more data needs to be coded, the overall size of the coding unit does not need to be changed, which greatly improves coding efficiency.