The entrance/exiting of converter is one of the key techniques of UHVDC project.When telecommunication between stations is lost,the exiting of one converter at rectifier side due to fault sometimes would cause overvoltages of the rest converter in series.In this paper,the overvoltages are analyzed from the perspective of control strategy and an optimized strategy,which adjusts the voltage reference at rectifier side and current margin at inverter side respectively,is purposed.The real time digital simulator (RTDS) simulation results prove that the optimized strategy can effectively suppress the overvoltages under the circumstances mentioned above and can be adopted in future UHVDC projects.