Abstract: Due to the ability of stabilizing voltage and frequency for weak/passive system, modular multi-level converter based HVDC（MMC-HVDC） has becoming a feasible approach for weak grid/offshore wind power delivery. Broadband oscillations were reported in certain number of MMC-HVDC projects with wind power, the mechanism and analytical method are urgent issues for studying. This paper established mathematical model between the sequence impedance of permanent magnet synchronous generator（PSMG）/double fed induction generator（DFIG） and their controller parameters, the influence of parameters on the sequence impedance characteristics were also studied. Sequence impedance model for MMC-HVDC was established, its broadband impedance characteristic was analyzed as well; Boundary condition of oscillation was proposed by maximumpeak-criteria-based Nyquist stability criterion, which was used to reveal broadband oscillation mechanism for wind farm integration through MMC-HVDC. Based on time-domain simulation based on control hardware in the loop（CHIL） simulation platform and frequency domain scanning of impedance, the oscillation mechanism and its analytical method are validated.