A blade type compressor comprises a cylinder, a rotating shaft, a rotor, blades, blade troughs, a side board, a discharging chamber, a back pressure chamber and a back pressure supplying channel, wherein the back pressure chamber is limited by the bottom surfaces of the blades and the corresponding blade troughs. The back pressure supplying channel extends from the discharging chamber to the back pressure chamber. The back pressure chamber comprises a shaft side expansion chamber, an upstream channel, a downstream channel, a board side expansion chamber, an opening and a rotating channel. The opening allows connection between the board side expansion chamber and the back pressure chamber. Along with rotation of the rotating shaft, when the shaft side expansion chamber is connected with the upstream channel through the rotating channel, the shaft side expansion chamber is disconnected with the downstream channel. Along with rotation of the rotating shaft, when the shaft side expansion chamber is connected with the downstream channel through the rotating channel, the upstream channel is disconnected with the shaft side expansion chamber.