Abstract: The theory of multiple correlations was adopted in structural system reliability analysis for the first time and the recursive formula of equivalent function for parallel system was deduced, and multiple correlation-equivalent plane method was presented. The method solves the problem that equivalent principles of equivalent plane method don't include the correlation information, and overcomes the lack of great error of equivalent plane method used in parallel system reliability. The result proves that the method has high accuracy and is better to traditional structure system analysis method, and is suitable for large structural system reliability analysis.