The utility model discloses a high-precision anti-interference excitation power supply for a ground screen flaw comprehensively-diagnosing system in a transformer substation. The excitation power supply consists of an input filter circuit, a rectifying filter circuit, an inverter, an output rectifying filter circuit, an auxiliary power circuit, a control circuit, a protection action circuit and a detection circuit. When in work, after passing through the input filter circuit and the rectifying filter circuit, 380 V AC achieves the transformation from DC to AC, the rectified DC is changed to be DC, and finally a stable and reliable DC can be provided after output rectification and filtration according to the needs of load. The excitation power supply is used for the ground screen flaw comprehensively-diagnosing systems in transformer substations, and has the advantage of reasonable structure design, small volume, convenient use, high output of current and power, wide voltage variation range, good interference resisting capability, easy achievement of automatic transmission and the like.