The invention discloses a power battery plug-in ammeter and an electric metering method thereof in an electric vehicle switching mode. A bottom housing, an upper cover and a PCB of the ammeter are respectively provided with an anode through hole, a cathode through hole and a grounding electrode through hole. The anode through hole of the upper cover is internally provided with an anode contact elastic sheet connector which is used for voltage anode sampling. The cathode through hole is internally provided with a cathode contact elastic sheet connector for voltage cathode sampling. The anode through hole on the PCB is provided with a straight-through current sensor. The bottom housing is provided with a plug-in type connector which is used for connecting with all light current signal interfaces of a pinhole coupling type battery box connector plug. The upper cover is provided with a light current signal adapter which is used for connecting with all interface slots of a pinhole coupling type battery box connector socket. The power battery plug-in ammeter and the electric metering method thereof have advantages of settling an existing problem of power battery energy consumption metering in the electric vehicle switching mode, realizing quick mounting on a standard power battery, and realizing quick changing and in-time metering.