The invention provides a device for suppressing sub-synchronous oscillation, sent out through series compensation, of a power grid side of a new energy base. The device comprises a signal extraction module, a signal processing module and a voltage source converter, wherein the signal extraction module, the signal processing module and the voltage source converter are sequentially connected, an input end of the signal extraction module is connected between a convergence station of a new energy power generation base and a series compensation sending-out system, and an output end of the voltage source converter is connected with an external power transmission line of the convergence station. Compared with the prior art, the device for suppressing the sub-synchronous oscillation, sent out through series compensation, of the power grid side of the new energy base, provided by the invention, has the advantages that a large number of draught fans can be prevented from disconnecting with the grid due to sub-synchronous oscillation after a large-size new energy wind power base is connected to the grid through the series compensation sending-out system, and thus, the safe transmission and the stable running of new energy power are ensured.