Flexible low-frequency transmission has a broad application prospect in offshore wind power grid-connected scenarios, but there is a risk of broadband oscillation caused by the interaction of power electronic equipment. In this paper, a method for analyzing the influence factors of broadband oscillation based on multiple linear regression is proposed. Firstly, a low-frequency transmission system model based on modular multilevel matrix converter (M3C) is established, and the Nyquist criterion is used to judge the stability of the flexible low-frequency transmission system of offshore wind power under different parameters. Then the multivariate linear regression coefficient is obtained based on the least square method and the significance test is carried out. Finally, the influence weights of each parameter on the broadband oscillation of the system are obtained. The permanent magnet synchronous generator (PMSG) grid-connected via flexible low-frequency transmission system is built in the electromagnetic transient simulation software PSCAD/EMTDC. The simulation results verify the effectiveness of the proposed method.