The intensity of the spring was adjusted with finite element method and the distributive laws of stress field and displacement field were obtained. Thus the maximum shear stress was got through the formula of spring intensity. So, two methods on analyzing the stress of cylinder spiral tension spring were introduced in this paper. One is the finite element method; the other is the formula of spring intensity. Then analyzing the spring deformation under load clarifies the function of the finite element method upon spring design, selection and strength check, and improves the reliability of spring design and shortens design time.