A lawn mower includes an electric motor, a driving assembly coupled to the electric motor, a blade assembly coupled to the driving assembly, a battery for providing electricity to the electric motor, a switch unit electrically connected to the electric motor and the battery, and a detecting unit. The detecting unit includes a sampling resistor electrically connected in series with the battery, and a trigger circuit electrically connected in parallel with the sampling resistor and configured to control the switch unit to make or break electrical connection between the electric motor and the battery according to detected voltage across the sampling resistor.
