In order to solve the non-compatible problem between the general monitoring equipments of substation or non-substation equipments with substation internal monitoring system of IEC 61850 standard，this paper proposes a new method for the conversion module between Modbus communication protocol and IEC 61850-8-1 standard.At first，this paper analyzes the information model of IEC 61850 and of MMS;and by use of the object-oriented technology，an information model of Modbus RTU is built，which establishes the information model mapping relation among Modbus，IEC 61850 and MMS based on the principle of layered semantic correspondence;and then，based on the proposed model，a conversion module between Modbus and IEC 61850-8-1 standard is established;finally，an information model for the interval controller is built as an example.Based on the technology like MMS-EASE LITE and so on，this paper achieves the main objective of communication protocol conversion，and realizes the reading and writing service of measurement data such as phase current，which verifies the correctness and feasibility of the proposed method.