The Cellular Automaton (CA) is a kind of discrete system whose dynamic performance depends on simple reactions among single cells.It has been widely applied in many fields nowadays because it can mimic some intricate situations.The present designs of cellular automaton,however, are mostly such systems with stationary cell size.In particular cases, there could be some huge differences between simulation and real statistics.The CA model with variable cell size (CA-VCS) then becomes significant, and the design for extended CA based on the existing model is proposed to simulate the movement of passengers in subway.In most cases, the cell size is referred to psychological size not actually physical body size.With the consideration of high density in subway in rush hours, Cells could alter its cell size based on the normal CA models to describe passengers much accurately according to the condition around.When meeting highly dense population, cells will be compressed and transformed into small size until they could find enough space to enlarge their size.The simulation based on the defined movement rules of cells shows the necessary processes for the cell transformation.The relative research and its results provide the proof to apply the proposed model in analysis of subway.