The IMA platform has such characteristics as time correlation, function dependence, multiple states and numerous parts. To solve the difficulty of the IMA platform in reliability analysis, a method for Discrete Event Evolution Tree (DEET) simulation analysis was proposed.In the running process of the IMA platform, the random failure event was transformed into a discrete failure event sequence, so as to drive the constant evolution of the system state. The evolution tree of the failure event was used to analyze the impact of the discrete failure event on the system state. Then, the multi-state sets and large sample observation were set up to evaluate the probability of the IMA platform being in different states at different time. The DEET method can quantitatively analyze the multi-state reliability of the IMA platform and serve as a theoretical data basis for further design.