The invention discloses a protection switching system and method combining branch protection and line protection in an optical transport network, and relates to the field of electric layer protection switching in the optical transport network. In the system, a slave branch port is added in a network element branch side. The method comprises the following steps that: when a cross board card detects an alarm during protection switching of the system, if the alarm is generated by a master branch port, the slave branch port receives a service and transmits the service to a working line port and a protection line port concurrently; if the alarm is generated by the working line port, the protection line port transmits the service to the master branch port and the slave branch port concurrently; and if the alarm is generated synchronously by the master branch port and the working line port, the slave branch port receives the service and transmits the service to the working line port and the protection line port concurrently, and the protection line port transmits the service and transmits the service to the master branch port and the slave branch port concurrently. Through adoption of the protection switching system and method, the service can be switched to the slave branch port in order to perform a communication without causing any long-time communication interrupt, thereby enhancing the security performance of a network.