The utility model relates to an electrical technology field specifically is a circuit structure of power frequency automatic switch -over is arrived in frequency conversion of boiler fan, and the power frequency operation can be arrived by the automatic switch -over in the boiler fan frequency conversion trouble jump vehicle -hour to brief, the easy control of this circuit structure flow, guarantees boiler fan continuous operation. The utility model discloses a circuit structure of power frequency automatic switch -over is arrived in frequency conversion of boiler fan, user's switch, converter and boiler fan that connects including the electricity, its characterized in that: still connect the automatic power frequency bypass at the converter both ends including the electricity, this automation power frequency bypass and with the converter all with the control system of boiler connects.