The invention belongs to the technical field of fluid tightness testing and relates to a transformer substation gas leakage detection mobile platform. The transformer substation gas leakage detection mobile platform comprises a dolly. A gas leakage detection component is installed on the dolly through a holder. A control device and an industrial control computer are installed inside a dolly body. A drive motor, a navigation assembly and a fixed point detection component are installed on the bottom of the dolly. The drive motor drives hubs to rotate. Sensing tracks are installed in the transformer substation corresponding to the navigation assembly. Marked points are installed on the sensing tracks corresponding to the fixed point detection component. The navigation precision is high, and the safe and reliable operation of the transformer substation equipment is ensured. The invention further discloses a detection method of the transformer substation gas leakage detection mobile platform. After coarse detection marked points and fine detection marked points are determined, the dolly firstly reaches the coarse detection marked point to test the equipment coarsely, if no leakage is detected, the dolly continuously goes to the next coarse detection marked point to carry out testing, if a suspicious leakage is found, the dolly is controlled to reach corresponding fine detection marked point to carry out fine testing, the test precision is high, and the result is safe and reliable.