The utility model discloses a diesel engine for a heavy duty car which adopts EGR and particulate trap technique and meets the IV national emission standard, comprising an electric control common rail fuel injecting system, an exhaust gas recirculation EGR system, an exhaust post-processing system and an on-board diagnosis OBD system. The exhaust gas recirculation EGR system is arranged in an exhaust system in the engine; the exhaust post-processing system is arranged outside the engine and includes a diesel engine oxidation catalyst DOC and a particulate trap; and the diesel engine oxidation catalyst DOC and the particulate trap are in series connection in a silencer. The utility model has the beneficial effects of low cost in the structure configuration, low requirement for the using environment and wide application range; and the diesel engine for the heavy duty car meets the requirement of using the diesel engine in China.