The invention provides an active supporting device for preventing rollover of a rail transit vehicle caused by derailing. The device comprises a cylinder body and a supporting column, wherein the cylinder body is provided with a piston cavity; the inner wall of the upper end of the cylinder body is provided with an upper clamping groove; the inner wall of the lower end of the cylinder body is provided with a lower clamping groove; the supporting column is movably arranged in the cylinder body; the upper end of the supporting column is provided with a piston plate; the piston plate is in sealed contact with the inner wall of the cylinder body; the side wall of the piston plate is telescopically connected with an elastic block; the elastic block is clamped in the upper clamping groove or the lower clamping groove. According to the active supporting device for preventing rollover of the rail transit vehicle caused by derailing, the vehicle can be supported by extending the supporting column of the vehicle out under the condition that the vehicle has the rollover trend, the vehicle rollover accident is avoided, and the safety of the vehicle is effectively protected.