The invention provides a switch locking method of a high-voltage direct current convertor station, comprising the following steps of: realizing switch locking on an I/O interface board operated by a direct current control switch in a direct current control protection system, analyzing commands, such as a switch closing command and the like from each control protection host, by a communication module, sending the commands to a CPU module, and receiving commands of controlling and protecting each subsystem send by a field bus by the CPU module; outputting closing signals to switch equipment by connecting the switch closing command and the input end of an and gate; arranging an RS trigger to be connected with received switch locking judgment; when the I/O interface board receives any one switch locking command but does not receive an unlocking command, outputting the switch signals needed locking by the Q end of the RS trigger; when receiving the unlocking command by the I/O interface board, prohibiting outputting the locked switch signals by the Q end of the RS trigger, and connecting the Q end and the other input end of the and gate through a not gate. The invention protects the safety of primary equipment of the direct current convertor station and has simple realization method without increasing the design complexity of the control protection system.