Abstract: By comparatively analyzing causes and characteristics of a city metro train operation delays over 5 minutes, the fault mode and reliability of different train control system modes are analyzed and calculated with model. Based on Colored Petri Network (CPN) modeling method, the influence of CBTC+BM and CBTC+TBTC system downgrading mode on train operation delay is simulated for analysis. Results show that when the BM design headway is relatively short, operation delay can be controlled under 5 minutes; when the TBTC design headway is around 100 s, operation delays will not exceed 2 minutes. The analysis of the impact of different train control system modes reliability and communication fault on operation delay can be a reference for rail transit signaling system design, signaling format selection and practical operation.