Abstract: Aiming at the mechanical properties of variable stiffness spring, the influence of geometric parameters on the mechanical properties of variable stiffness helical spring with bell type was studied. Based on the series theory of spring, a design method of bell-type variable stiffness helical spring is proposed. A three-dimensional model of variable stiffness helical spring is established through parametric modeling. The correctness of theoretical calculation and finite element model is verified by static compression test, and the maximum error between simulation and actual measurement is less than 10%. The influence of key geometrical parameters such as linear diameter, pitch and effective number of turns on the mechanical properties of the variable stiffness helical spring is analyzed by the finite element software Ansys. The analysis results provide a reference for the design and optimization of the variable stiffness helical spring.