The invention discloses a rail defect detecting method and system and a vehicle. The system comprises a magnetizing device for magnetizing a rail, a magnetic sensor for collecting magnetizing information of the rail, a positioning device for obtaining position information of a rail flux leakage position according to a positioning instruction sent by a controller, a display device, the controller connected with the positioning device, the magnetic sensor and the display device and used for judging whether flux leakage happens or not according to the magnetizing information of the rail, conducting defect recognizing and contour inversion on the magnetizing information during flux leakage and sending the result to the display device to be displayed. The magnetizing device, the magnetic sensor, the positioning device, the display device and the controller are all arranged on the same carrier. The system has the advantages that all the detecting devices are arranged on the same carrier, and by detecting and analyzing rail defects in a magnetizing mode, the system is low in power consumption, high in response speed, high in detection accuracy, high in positioning accuracy, long in runtime and capable of displaying positions and shapes of defects in real time.