Abstract: On the basis of engineering weighting factor assignment method, a new reliability research approach is suggested for index decomposition of system and components. Based on the platform screen door system operation data of phase 1 project of Zhengzhou Metro Line 1, from aspects including system division, function block diagram, index decomposition, the difference between actual value and target value is analyzed, and a series of effective measures for optimization is formulated. Reliability verification results show that the reliability optimization carried out with this approach prominently lowers system malfunction rate and is able to fulfill targets, thus effectively improving system reliability.