The disclosure provides a power tool, a detection circuit and a detection method of a load state thereof. The detection circuit of the power tool includes: a main control unit, a sampling resistor, a voltage sampling unit and an alarm display unit. The sampling resistor is arranged on a driving loop of a motor. The voltage sampling unit is used to sample a voltage across the sampling resistor. The alarm display unit is connected with the main control unit. The main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor sampled by the voltage sampling unit.