After studying the measurement method of peroxide concentration by iodometry, the decomposition kinetics of five types of peroxides were investigated in detail. On the basis of the additive property for rate, a decomposition kinetic model of peroxide mixtured initiator has been deduced. The model values of decomposition rate constant coincided with the experimental data. The kinetic behavior of the vinyl chloride suspension polymerization with peroxide mixture as initiators can be predicated by using the model of decomposition rate constant of peroxide mixture and simulating the model of vinyl chloride polymerization. After studying the measurement method of peroxide concentration by iodometry, the decomposition kinetics of five types of peroxides were investigated in detail. On the basis of the additive property for rate, a decomposition kinetic model of peroxide mixtured initiator has been deduced. The model values ​​of The kinetic behavior of the vinyl chloride suspension polymerization with peroxide mixture as initiators can be predicted by using the model of decomposition rate constant of peroxide mixture and simulating the model of vinyl chloride polymerization.