Aiming at the problems of complex faults, outdated maintenance methods and lagging maintenance manual in the maintenance work of EMU coupler, an auxiliary maintenance method of EMU coupler based on mixed reality technology was proposed. With the help of mixed reality and data interaction technology, the overall model and technical framework of MR auxiliary maintenance for the fault of EMU coupler were constructed. The key technologies such as virtual-real registration fusion, intelligent fault diagnosis, data information interaction and maintenance assistance guidance were studied, and various human -computer interaction assistance maintenance methods such as gesture recognition and eye tracking based on Unity3D-HoloLens were realized.