The invention provides a saw blade bearing and clamping device with an automatic centering function. The saw blade bearing and clamping device comprises a mounting base, a driver, a stationary shaft sleeve, a sliding shaft, a first butting block and a centering alignment mechanism. The stationary shaft sleeve is provided with a hollow structure with two ends open, and arranged on the mounting base. The driver is arranged at one end of the stationary shaft sleeve, the sliding shaft is slidingly arranged in the hollow structure of the stationary shaft sleeve, one end of the sliding shaft is connected to the output end of the driver, the other end of the sliding shaft extends out of the other end of the stationary shaft sleeve to form a bearing end, and the first butting block is detachably mounted at the bearing end. The centering alignment mechanism comprises an elastic part and a bearing sleeve part, one end, away from the stationary shaft sleeve, of the bearing sleeve part gradually diminishes towards the direction away from the stationary shaft sleeve to form a reducing surface bearing portion, the bearing sleeve part is sleeved on the sliding shaft slidably, the elastic part constantly drives the bearing sleeve part to move toward the direction away from the stationary shaft sleeve, and a saw blade is sleeved on the reducing surface bearing portion and clamped between the stationary shaft sleeve and the first butting block.