The integration of Functional safety has been more and more important in the industry automation, especially for servo drives. So the communication protocol for the control system should support Functional safety. EtherCAT is a real time industrial Ethernet protocol with high performance, which also specifies Functional safety profile. This paper firstly describes the safety integrated servo drive and its safety functions. Then, the FSOE is studied, which communication principle is demonstrated with a functional safety example for servo drive control.