Abstract: In order to analyze the influence of the interaction between the weak grid and the inverter on the stability of the new energy grid-connected system, this paper divides the current loop open-loop transfer function G₀, which is characterized by the closed-loop stability performance of the system, into three links. The three links of impedance, phase-locked loop and current controller are multiplied, and the equivalent loop ratio expression is obtained by combining the phase-locked loop and the grid impedance link and divided by the current controller. The grid-connected inverter control loop stability criterion is proposed based on Nyquist's theorem. When the amplitude of G₀ numerator and denominator are equal, the amplitude-frequency curve would generate an intersection point, which is easy to make the system closed-loop gain infinite and unstable. Then, in order to analyze the interaction law among the three links, this paper derives the expression of the bandwidth ratio n of the phase-locked loop and the current controller that satisfies the stability criterion. When the critical value is n, there will be an interaction between each link, which is mainly represented by the overlap of the G₀ numerator and denominator amplitude- frequency curves in the Bode plot. The weaker the power grid or the closer the PLL and the current controller bandwidth are, the larger the overlapping area of the frequency curves, the easier it is to cause the closed-loop gain to be infinite, that is, the more likely the system is to be unstable; in addition, when the current controller bandwidth is fixed, the critical value of n is between less than 1 and greater than 1 as the power grid weakens. The bandwidth ratio of the phase-locked loop to the current controller is greater or less than 1, which can make the system remain stable. Finally, the accuracy of the theoretical analysis is verified by Matlab simulation and HIL experiment.