In recent years, with the rapid development of DC technology and the increasing capacity of wind power connected to the power grid, wind power systems integrated into DC distribution systems have become an effective mode of absorbing new energy generations. This paper constructs a small disturbance stability model for a direct-drive wind power system in the DC distribution system, the oscillations relationship of key equipment are investigated by the eigenvalue and modal analysis method. Then the influences of synchronous motor parameters, PLL control parameters and DC / DC converter control parameters on the system operation mode, and dynamic interaction between wind power system and VSC are observed based on the proposed model. It provides a better understanding about multi-time scale oscillation research of flexible DC distribution system.