The utility model relates to the technical field of the power supply, particularly to a power supply for a high-voltage on-line detection device. A power frequency power supply is processed by AC-DC-AC conversion and frequency demultiplication, high-pass filtering, low-pass filtering, and pushing and amplifying at a low-voltage side to obtain a single-frequency high-frequency electric power and the single-frequency high-frequency electric power is fed into an electric energy sending coil; the electric energy sending coil transmits the electric energy to an electric energy receiving coil by an electromagnetic coupling device; the electric energy receiving coil transmits the received alternating-current electric energy to a direct-current conversion circuit; the direct-current conversion circuit carries out conversion to obtain a direct current and then power is supplied for the high-voltage on-line detection device. On the basis of the magnetic resonance principle, one insulating material is used for manufacturing a resonant cavity and thus reliable transmission of the electric energy from the low-voltage side to the high-voltage side can be realized, thereby ensuring that no direct power connection exists between the high-voltage side and the low-voltage side. Compared with the method of energy transmission by the multi-level structure-based relay transmission coil in the prior art, the provided power supply has characteristics of simple structure, convenient debugging, high reliability and durability, and high transmission efficiency.