The invention discloses a pile-soil contact surface shearing mechanical-characteristic testing device which comprises a supporting device, a pressure chamber, a pressure device, multiple thrust devices and multiple horizontal fixing devices. The supporting device comprises a frame, a supporting plate and a counter-force frame arranged above the supporting plate. The pressure chamber is arranged onthe supporting plate and comprises a top plate, a base plate and multiple outer-side vertical plates slidingly arranged between the top plate and the base plate, the base plate, the top plate and themultiple outer-side vertical plates jointly define a cavity for containing a pile sample and a soil sample, and the horizontal cross section of the cavity can be adjustable in size. The testing device can exert horizontal thrusts to different sides of the pressure chamber through the multiple thrust devices so as to exert horizontal forces to the sides of the pile sample by extruding the soil sample, and can effectively simulate the pile foundation stress working conditions under the situation that soil body pressures exerted in different directions around a pile are different and make the working conditions have high similarity with actual working conditions. The testing device can test pile foundations of round and square piles and the like with regular-shaped cross sections.