Abstract: The communication protocol of a smart substation control level deeply depends on the third party protocol stacks with poor autonomy and controllability, which is particularly unfavorable for the security of the power grid under the critical international conditions. In this case, the service oriented protocol based on IEC 61850 is designed. In service mapping, the protocol directly maps the abstract communication service interfaces to the TCP/IP protocol stacks, improving the service performance. The protocol standardizes all the syntax definitions of the abstract communication service interfaces based on IEC 61850-7-2. It extends the service interfaces such as the association and the remote invocation, ensuring the communication security between the client and the server and making up for the support services to the master station. In terms of coding, the ASN.1 PER coding is adopted to enhance the efficiency of message encoding, decoding and data transmission. According to the above designing, the software package of the service oriented protocol is developed and tested, and compared with the MMS protocol. The test shows that the length of the message transmitted by the service oriented protocol is reduced by about 20% compared with that of the conventional standardized ones, and that the processing time between the requesting and responding service is reduced by more than 50%, which effectively improves the interaction performance and efficiency.