Abstract: A geo-entity based cellular automata model of infectious diseases is presented.Through the model the authors develop visual simulation program in GIS environment，and give out the simulation results of two typical spread dynamics of local contagion and global contagion（due to the existence of roads）.The analysis for the results show that the reasonable results can be gained with neighbor patterns suitable for the epidemiological characteristics.Coupled with the functionalities of spatial analysis and visualization of GIS，the proposed cellular automata model can visualize the epidemic procedure of infectious diseases，ascertain the key parameters that affected the spread of diseases，evaluate the effect of some interventions（such as vaccination，isolation and so on），and calculate the information of spatial distribution and statistics of epidemics.Consequently，provide decision makers with scientific clues.