The invention provides an onsite stable-state short circuit characteristic test method of a large phase modifier and transformer group, and belongs to the technical field of motor test. The invention provides the stable-state short circuit characteristic test method used in a running-out state, and aims at solving the problem that a large phase modifier is started by a frequency-variable starting device, a stable rated rotating-speed short-circuit state cannot be maintained, and further the stable-state short circuit characteristic of the large phase modifier and transformer group cannot be tested in a routine method, The method can be used to solve problems in onsite stable-state short circuit characteristic test of the large phase modifier and transformer group, and has significance in safe, efficient and reliable operation and maintenance of the large phase modifier.