Abstract: A grid-tied converter connected to weak grid is prone to cause oscillation problems in the grid-tied system. Therefore, this paper proposes an admittance reshaping control strategy based on passivity theory to improve system stability performance, so that the grid-tied system is not affected by the equivalent impedance of the grid in low and middle frequency bands. First, in order to facilitate the construction of a strictly positive real converter admittance matrix, the converter admittance model is decomposed into two subsystems for analysis to identify reconfigurable control links. Then based on the positive real method, the outer loop remodeling matrix M and the inner loop remodeling matrix N are designed to gradually stabilize the grid connected system in the middle and low frequency bands. In addition, the admittance remodeling system is a symmetric system (a single-input single-output system), which simplifies the analysis of stability and resonance problems in the case of multiple converters. Both simulation and experiment verify the feasibility and effectiveness of the proposed admittance remodeling method in improving system stability and simplifying system stability analysis.