Abstract: Developing the reliability modeling, analysis and assessment technology with respect to multistate complex equipment system plays an important role for reducing risk in development, optimizing construction of support system, and improving efficiency in use. The regular reliability analysis and assessment system use Markov processes to deconstruct multistate transition. However, the modeling subjects to limitations on precision and credibility. Breaking the exponential distribution hypothesis, a new system to model, analyse and assess multistate reliability using semiMarkov processes is established and applied to assess multistate reliability about the strong electromechanical coupling marine generator. Research shows that the new solution system can effectively promote assessment precision and data credibility for multistate complex technical system with the characteristic of strong electromechanical coupling, can effectively avoid risks during the design and the usage phases, and can make more rational decisions for the support system. Moreover, the results have an important value in theoretical analysis and engineering application for the designers and the users.