Abstract: The high proportion of wind power access is easy to induce sub-synchronous oscillation in the directdrive wind power network system. Accurate location of the oscillation source is the basis for implementing effective countermeasures. In this paper, the location method of subsynchronous oscillation source in direct-drive wind power interconnection system based on transient energy flow method is studied. Aiming at the deficiency that synchronous phasor measurement cannot accurately measure sub-synchronous oscillation information, the mathematical model of direct-drive wind turbine is constructed, and the calculation method of transient energy flow suitable for subsynchronous oscillation is proposed. The correlation mechanism between the dissipated energy in the transient energy of direct-drive wind turbine and the oscillation mode and damping characteristics of the system is revealed,and the applicability of transient energy flow method to the location of sub-synchronous oscillation source in directdrive wind power interconnection system is demonstrated. Based on EMTDC/PSCAD platform, a multi-machine grid-connected simulation system of direct-drive wind turbine is built.The simulation verifies the effectiveness of the proposed sub synchronous oscillation source location method based on transient energy for direct-drive wind power interconnection system.