Abstract: The temperature filed of 22CrMoH billets in continuous casting was simulated by using a moving boundary method. Based on a CAFE (cellular automaton-finite element analysis) approach, the microstructure of 22CrMoH billets was obtained and it agrees reasonably well with experimental data. The effects of alloying elements such as Cr, Mo, Si and Mn on the microstructure of 22CrMoH billets were studied. The results suggested that within the specified scope of the 22CrMoH grade, with the contents of Si and Mn increasing, the proportion of equiaxed grains increased, and the number of grains raised, hence the average radius reduced. The increased content of Mo tends to enhance the formation of nuclei, and a proper decrease of Cr element is conducive to raise the ratio of equiaxed grains while has little influence on the number and average radius of grains. Finally, the contents of Cr, Mo, Si and Mn in 22CrMoH steel was optimized, and the simulated results show that the microstructure of 22CrMoH billets is greatly improved:the proportion of equiaxed grains becomes near double, the number of grains increases by 19.96%, and the average grain radius decreases by 9.20%.