In order to improve the applicability of response fault diagnosis for variable valve timing(VVT) system of hybrid engine, an online diagnosis strategy was proposed based on the accumulative value of VVT action deviation. Based on the sum of absolute values for angle change in all calculation cycles of the statistical window, different fault states were characterized by the proportional coefficient of the deviation accumulated value between the actual and the target position of VVT so that the diagnosis process was no longer limited by the range and variation of VVT operation. The real vehicle verification results showed that the accurate diagnosis could be achieved in the three states of no-fault, stuck and slow response under the world-harmonized lightduty vehicle test cycle(WLTC). The fault reporting and repair functions of the onboard diagnostics system(OBD) could be executed normally on the actual urban road. According to the test results under the responselimit state, the stuck fault threshold was set to 8% and the slow response fault threshold was set to 50%. The statistical analysis results showed that the setting of fault threshold met the 3σ standard, and hence there is no risk of misjudgment.