The invention relates to a GNSS positioning data health degree diagnosis method applied to rail transit. The GNSS positioning data health degree diagnosis method applied to rail transitcomprises the following steps that 1, GNSS data preprocessing is conducted, and then GNSS self-diagnosis is conducted to obtain a GNSS self-diagnosis result; 2, a rail electronic map is constructed, therail electronic map and data of GNSS perpendicular to the rail are used for rail electronic map assisted GNSS diagnosis to obtain arail electronic map assisted GNSS diagnosis result; 3, the axle sensor data are acquired, and the axle sensor self-diagnosis is conducted, and then the axle sensor data and date of the GNSS along the direction of the rail are used forconducting axis sensorassisted GNSS diagnosis toobtain an axis sensorassisted GNSS diagnosis result;and 4,the GNSS self-diagnosis result, the rail electronic mapassisted GNSS diagnosis result, and the axle sensorassisted GNSS diagnosis result aredetermined toobtain a GNSS health degree diagnosis result. Compared with the prior art, theGNSS positioning data health degree diagnosis method applied to rail transit has the characteristics of beingsafe and reliable, high in diagnostic precision, and having less trackside devices.