Abstract: Multi-converter systems with high penetration of phase-locked loop synchronized converters are prone to have transient synchronization instability under large disturbances. In order to ensure the stable operation of the multi-converter system after large disturbances, it is crucial to study the interaction mechanism between converters on transient synchronization stability of the whole system. To this end, this paper took the paralleled- converter system as an example, and built a transient interaction model. It can be found that the interaction between converters was determined by the mutual-impedance voltage drop, mainly affected by different current injection angles during the fault. On this basis, with considering the dynamic characteristic of the interaction between converters, the interaction mechanism was revealed based on equal area criterion (EAC). The effect of different current injection angles on transient synchronization stability of the system was quantitatively analyzed. The research result shows that transient synchronization stability of the paralleled-converter system can be significantly enhanced when the mutual- impedance and self-impedance voltage drop have opposite signs. Finally, the corresponding model was provided in PSCAD/ EMTDC and RT-LAB hardware-in-the-loop experimental platform to verify the correctness of theoretical analysis.