The automation level of replacing highspeed shaft bearing of the wind turbine generator system in the air is low,the study on automatic replacement of bearing device is relatively few.A device was designed by which shaft bearing replacement could be realized automatically in the air.Through controlling the hydraulic system of the electorhydraulic automatic replacement device,not only the technological requirements in the process of bearing dismantling and assembling could be met,but also automatically dismantling and assembling highspeed shaft bearing could be realized.Moreover,the needs of cabin spatial structure could be met and the working efficiency of dismantling and assembling shaft bearing was improved.Due to the characteristics mentioned above,on one hand,the number of cabin staff may be decreased from five to one to two,which can lower the labor intensity of the operator;on the other hand,the safety performance can also be improved.The device has many features,such as large system powertoweight ratio,large system stiffness,good structure stability and easy installation and so on.