In order to solve the problem of incompatibility among DTUs from different manufacturers, and to achieve good interoperability between the DTU and other IED equipments, IEC 61850 is adopted to establish DTU models. IEC 61850 standard, the international communication standard on substation automation system, is designed to unify the substation automation communication systems. Basing on IEC 61850, the paper realizes functional analysis of the DTU, adopts the object- oriented modeling approach to establish the DTU information model, and analyzes information exchange between logical nodes. In the end, the paper takes the GetDataValues service as an example to analyze the mapping progress from the ACSI service to the MMS service, providing a basis that the DTU can achieve good interoperability basing on IEC 61850