The invention discloses an adaptive tensioning supercharger test device, which solves the problem that a belt tensions unreasonably. At a low rotating speed, the tension required by a belt is small, the pressure at the outlet of a supercharger compressor is low, and the pressure acting on the adaptive tensioning belt is also low; at a high rotating speed, the tension required by the belt is increased, the pressure at the outlet of the supercharger compressor is correspondingly increased due to the improvement of the rotating speed, and the pressure acting on the belt through the adaptive tensioning belt device is also increased, so that the pressure required by slippage of the belt is avoided and the transmission stability and the transmission efficiency are improved; in addition, by adopting the test device, the test requirement of a supercharger under full conditions can be met, the pneumatic performance and the mechanical efficiency of the supercharger can be deeply studied, and a test guarantee is provided for mechanical pressurization research.