Abstract: In order to simplify the calculation of parallel redundancy operators, the characteristic value calculation method of GO operators was used to study the signal failure rate distribution characteristics of the parallel redundancy operators. The feasibility was validated that the repairable system with low-level redundancy could be hypothesized and treated as an exponential distribution unit. Then, an improved algorithm of the parallel redundancy operators in GO model was proposed and applied to the reliability analysis of urban rail transit vehicle's door system. The results show that for the input signal with exponential distribution, the output signal of parallel operator has a non-exponential characteristic; the improved algorithm can simplify the calculation process of the reliability analysis of urban rail transit vehicle's door system by eliminating 10 intermediate variables and 3 calculation steps in the original algorithm.