Islanded operation of the DC sending system can reduce the impact of DC fault on the main system，thus enhancing the security of the system and increasing the capacity of the transmission corridor.In the islanded sending system of Yunnan-Guangdong DC transmission system，there are dynamic stability problems because the Xiaowan plant and Jin'anqiao plant are far away from Chuxiong converter station.The conventional power system stabilizer（PSS）effectively increases the damping of the oscillation mode between Xiaowan generators and Jin'anqiao generators，but exerts an adverse impact on the overvoltage control of the islanded system.This paper analyzes the cause according to the principle of the conventional PSS，then proposes a solution scheme using wide-area signals based PSS.The wide-area PSS based on the speed difference of generators can improve the dynamic stability of the islanded system，while avoiding the adverse impact on the overvoltage control.It has good feasibility in the islanded Yunnan-Guangdong DC sending system.The effectiveness of wide-area PSS is verified by simulation results.