Abstract: The time evolution of particle size distribution (PSD) is of fundamental interest and a key issue.PSD along with time is described by general dynamic equation (GDE).There is an antinomy of computation cost and computation precision in some ordinary Monte Carlo methods for GDE. A new multi-Monte Carlo (MMC) method is presented to consider GDE for simultaneous coagulation and condensation/evaporation of polydisperse particles.The MMC method is based on time-driven, constant number technique and constant volume technique.Firstly the MMC method is described in detail, including the setting of time step, the scheme of handling simultaneous coagulation and condensation/evaporation.Then the MMC method is validated by three kinds of special cases:constant coagulation kernel and constant condensation kernel(case1),constant coagulation kernel and linear condensation kernel(case2),and linear coagulation kernel and linear condensation kernel(case3).The simulation results of the MMC method for GDE agreed with analytical solution well, which proved that MMC method could resolve the contradiction between computation cost and computation precision, i.e., MMC method has both lesser computation cost and better computation precision.