Based on the OBD requirements of China Ⅵ emission regulation and OBD diagnostic principles, the components and functional modules for OBD system were analyzed. Then the fault characteristics and sensitivity of DPF under the faults of channel plugging, carrier damaging and fault solving were simulated based on AVL Boost simulation software and the corresponding diagnosis strategies were proposed according to the key functional diagnosis of OBD for DPF system under China Ⅵ emission standard. The results show that the temperature correlation before and after DPF and the pressure drop show a good sensitivity to each fault and can be used as an OBD diagnosis strategy to distinguish between the reasonable faults of differential pressure sensor and the abovementioned faults.