Abstract： The variation of cutting depth of the rolling cutter causes fluctuations of loads on the cutterhead. The variable loads result in fluctuation of stiffness after being transmitted to the contact surface between gripper and rocks, change the position and posture of the tunnel boring machine(TBM), and influence the loads on the cutterhead. The coupling of the loads and stiffness greatly influences the dynamic behaviors of TBM. Considering the fluctuation of loads on the cutterhead, the transmission of forces was analyzed using the parallel mechanism theory and the coupling of loads on the cutterhead. Besides, the stiffness on the surface between gripper shoes and rocks was studied. The results show that the stiffness on the contact surface increases with the enlargement of loads on the cutterhead. In mixed stratums, the stiffness fluctuates with the fluctuation of loads on the cutterhead. When the rocks at both sides are different, the average values and fluctuations of load on the cutterhead and stiffness of the contact surface increase compared with those of the same rocks at both sides, and the increase of stiffness on the hard contact surface is greater than the decrease on the soft contact surface.