Abstract: A set of high voltage direct current（HVDC） protection system setting system has been established in the engineering practice of HVDC in China for more than 30 years. For the complicated cases in application in recent years, this paper discusses the setting basis for the following protections: the starting setting of valve short-circuit protection needs to avoid the charging current of the resistance-capacitance circuit in parallel with the converter valve. And the over-current protection over-load section of the converter aims at the over-load target value of the DC operation current caused by the control failures, and the control target current exceeding the set running time. The setting of DC low-voltage protection threshold and delay-time should take into account the backup function of protection, and can not match with the long delay time period of the double-bridge principle of commutation failure protection. In addition, in-depth discussions are conducted on the coordination problems of setting between AC and DC systems, between DC protections in metal-return operating mode, and between high-voltage line restart and low-voltage restart.Finally, it is suggested that the setting and coordination between the setting values of HVDC transmission protection system should have certain standardization and moderate flexibility.