The invention provides a grounding detection protection method for a traction converter of a railway vehicle. The grounding detection protection method comprises the steps of a first step, judging whether the secondary side of a traction transformer is grounded or not, if so, blocking the traction transformer and the traction converter, otherwise, entering a second step; judging whether the auxiliary high-voltage side is grounded or not, if so, locking an auxiliary converter, otherwise, entering a third step; judging whether a PWMI/motor side is grounded or not, if so, locking a traction inverter, otherwise, entering a fourth step; judging whether the middle direct current link is grounded or not, if so, locking the traction converter, otherwise, entering a fifth step; and jugging whethervirtual grounding is formed or not, if so, locking the traction transformer and the traction converter, and otherwise, retuning to the first step. According to the method, the fault position of the traction converter grounding fault can be accurately positioned, and different protection actions can be adopted for different faults, so that potential safety hazards caused by only cutting off the traction converter when the secondary side output end of the transformer is short circuit is prevented, and the safety of the traction converter grounding fault protection is effectively improved.