The impedance of three-phase PWM converter is critical to its output character and also has influence to the whole system. The current research is mostly focused on the interaction caused by output impedance and the suppression method to the interaction. However, little literature paid attention to the output impedance itself. Using small-signal method, the impedance model of converter is established in the case of open-loop control and close-loop control considering the current loop and phase lock loop. The influence of introducing the current loop and the current control parameter on the rectifier output impedance is studied based on the small-signal model. The result shows that the introducing of current loop will reduce the amplitude of output admittance of rectifier. The decrease level in the low frequency range is mainly related to the integral parameter of current controller and the decrease level in the high frequency range is mainly related to the proportion parameter. The simulation result testifies the validity of the result. This work is supported by National Natural Science Foundation of China (No. 51277137, No. 51177113, and No. 51190102).