Abstract: In order to achieve precise control of robot joint stiffness and balance the intrinsic safety and high operational efficiency of robots, a design method of variable-stiffness actuator based on inverse proportional function curve groove(IPFC-VSA) is studied. Using a leaf spring as the elastic element of VSA, the roller is driven by a screw to move along an inverse proportional curve path, changing the effective length of the leaf spring to adjust its stiffness. The contour of the chute is modeled, simulated, and optimized to obtain parameters that balance stiffness range, linearity of stiffness curve, and structural feasibility. A prototype system is developed and experimental research is conducted. The experimental results show that IPFC-VSA has excellent stiffness control characteristics, with a nonlinear error of no more than 4% in its stiffness curve. It has a large range of variable stiffness and the ability to quickly change stiffness. In addition, the joint stiffness is decoupled from the deflection angle, effectively improving the controllability and accuracy of stiffness. Finally, it is verified that IPFC-VSA achieves intrinsic safety during the collision process by adjusting joint stiffness, through simulated collision experiments with the head.