The present invention provides a pneumatic motor with built-in striker mechanism, which mainly comprising: a cylinder, rotor set and output shaft lever; said rotor set consists of a rotary drum and flexible blades; said output shaft lever can be driven by the rotary drum; it is characterized by that, a chamber is formed into the rotary drum of the rotor set; a striking portion on the output shaft lever is located within the chamber, and the built-in striker mechanism is placed in the chamber, consisting of: striking bulges protruded on the striking portion, movable hammers sleeved externally on the striking bulge and struts axially located on the rotary drum; with this design, the present invention provides a new pneumatic motor with the striker mechanism set into the rotary drum of the rotor set, thus reducing greatly the axial length and volume of the pneumatic motor and realizing ease-of-use; moreover, the striker mechanism has advantages such as: direct driving by the rotor set, instant torque lifting and fast unlocking of components, thus saving substantially the cost of pneumatic motor with better economic benefits.