The invention relates to an inner hole thermal spraying device and method. Firstly, the sand blasting derusting and roughening treatment are performed on the inner wall of a pipe fitting; then, the pipe fitting is fixed within a chuck A, and a motor is started to enable a lead screw, a gear set and a rotating shaft to synchronously work, so that a spray gun bracket moves towards one side of a rotary clamping device in the central axis direction of the pipe fitting; when a port of an inclined section of a front end terminal is aligned with one end, far from the chuck A, of the pipe fitting, a paint nozzle is started, and when the front end terminal moves to one end of the chuck A, the spraying of a first layer is finished; and finally, priming coat spraying is performed on the inner wall of the pipe fitting by the same method and the inner hole thermal spraying device. The inner hole thermal spraying device and the method have the following advantages: the paint nozzle of the inner hole thermal spraying device is low in space utilization rate, and the inner hole thermal spraying device can spray the inner wall of a pipe fitting with a relatively small caliber, and is reasonable in structural design; and the device adopts mechanical connection at joints, so that free disassembly is achieved, and the device is simple in structure and low in cost, and solves the problems of the inner hole surface spraying of an existing thermal spraying technology.