<p>Continuous transient impact (CTI) frequently occurs in power split (PS) hybrid powertrain system when the mode transition torque crossing zero, which affects overall vehicle ride comfort. To study the CTI mechanism, a transient torsional vibration (TTV) coupling model of a hybrid powertrain test system is established based on the test bench with double feedforward correction load emulation compensation control, and realize the CTI performance prediction along the power transfer path. Firstly, the time-domain and frequency-domain characteristics of CTI during the mode transition process (MTP) test are introduced. Secondly, the external excitation model including bench load, engine resistance torque and motor torque ripple, and the internal excitation model including the torsional vibration of planetary coupling (PC) and two stage reducer are established. Then, the MTP coordinated control method of power split hybrid powertrain test system are introduced, and the gear torque zero crossing model which considering time-varying stiffness, damping and gear backlash is integrated into the TTV model. Finally, the CTI mechanism is simulated and analyzed. The results show that the front planet gear of Ravigneaux-PC is the main source of high-frequency gear knocking. Moreover, the frequent torque crossing zero at the dedicated hybrid transmission (DHT) power output end after the torque coordinated control of each power source is the main cause of continuous mesh impact during MTP, and the coupling effect with the gear backlash intensifies the CTI of DHT output end at frequency band 100–200&#xa0;Hz, and the CTI can reduce the overall efficiency of PS-DHT system and vehicle comfort. The research results are useful for the development of CTI suppression optimization algorithm.</p>