The invention discloses a power device for an amphibious vehicle. The device comprises a rotary shaft and a propeller, wherein the first end of the rotary shaft is sleeved with the propeller. The power device for the amphibious vehicle further comprises a synchronizer sliding sleeve, and the end, in the sliding direction of the first end of the rotary shaft, of the synchronizer sliding sleeve is fixedly connected with the propeller. According to the power device for the amphibious vehicle, the propeller and a vehicle power device are both arranged on the tail of the vehicle, in a flying mode, power is directly transmitted to the propeller by an engine, an intermediate transmission shaft is omitted, a power transmission line is simplified, and power becomes reliable and efficient; the power device for the amphibious vehicle is simple in structure and very practical.