The invention discloses a rail transport system with adjustable adhesion and an adhesion adjustment method thereof. The rail transport system comprises a transport vehicle and two supporting guide rails. The transport vehicle comprises a frame and wheels mounted on the frame and used for walking along the two supporting guide rails of a track. The supporting guide rails have pressure-bearing portions. The frame is provided with an adhesion adjusting device. The adhesion adjusting device comprises a pressurizing member for pressing the pressure-bearing portions to increase positive pressure between the wheels and the supporting guide rails. A pressurization adjusting device for adjusting a pressing force of the pressurizing member for pressing the pressure-bearing portion is arranged between and connected with the frame and the pressurizing member. The rail transport system has the advantages of capacity of preventing slippage, simple structure, low cost, stable and reliable operation,easy control and a wide application range. The adjustment method is to control whether to control and drive the pressurizing member to perform pressurization according to the result of comparison between a preset value and a rotation speed difference of driving wheels and driven wheels. The adjustment method has the advantages of little configuration, simple control, and good accuracy and timeliness of control.