Based on the traditional Q-V modal analysis method and considering the influence that a node’s active micro increment changes to the results of modal analysis, this paper uses the amended reduced order of Jacobian matrix to identify the system static voltage stability, adds PV nodes of reactive power of micro increment in the power flow equations to analyze the weak link in the system state of sampling, gets the involvement of voltage collapse of the generator nodes when modal analysis method is used to calculate node participation factor, which makes up for the deficiency that the traditional Q-V mode only calculates PQ node participation factor. The non-sequential Monte Carlo simulation method is combined to proceed random sampling of the state of the system and calculate the probability of the voltage collapse. IEEE-RTS 79 system is analyzed to prove the availability in the analysis of the weak link of the risk of voltage collapse using improved modal analysis technology.