The invention provides a handheld power tool, which comprises a handle assembly, a power mechanism connected with the handle assembly, and a working mechanism connected with the power mechanism. The power mechanism comprises a main housing, an inner housing, and a motor disposed in the inner housing. The main housing comprises a first air inlet at a side wall thereof, the inner housing comprises an opening. An airflow channel is located between the main housing and the inner housing, and in communication with the first air inlet, the opening and an inside of the inner housing. The handheld power tool of the present invention not only has good heat dissipation effect, but also has waterproof and dustproof effects, and can work in rainy days and humid areas without affecting the performance of the whole machine.