To evaluate the Possibility of subsynchronous oscillation between the turbine-generator unit and ±500 kV direct current transmission system from Baoji to Deyang, the unit interaction factor (UIF) analysis and complex torque coefficient method are adopted for risk assessment. The short-circuit capacities under typical operation modes at Baoji converter station ac bus are calculated using PSASP program,and the UIF shows that Baoji No.2 power plant extension unit doesn’t produce subsynchronous oscillation. Since the UIF of island operation mode in winter-base case is relatively larger to others, complex torque coefficient method is used to do time-domain simulation for Verification using electromagnetic transient simulation model in PSCAD/EMTDC. The results obtained from time-domain simulation conform to the unit interaction factor method. The analysis can be used as reference to subsynchronous oscillation problem resulted from direct current transmission system and power plant units nearby.