By simulating the reflection and refraction of single-ray at each interface of double-layer dielectric sphere, the force exerting on the dielectric sphere by a single ray is analyzed, and the force exerting on the sphere by the total Gaussian laser beam is calculated. The axial force is calculated when the refractive index of inner layer of double-layer sphere is 1.0 and 1.9, respectively, and then the influence of the refractive index of inner layer on optical tweezers trapping force is analyzed. As shown by the calculation results, the influence of different refractive indices and radii of inner layer on trapping force is notable. As the refractive index of inner layer is smaller than that of the outer layer, the stability of optical trapping is improved, but the spatial scale of trapping is reduced. And the performance of optical trapping is reduced as the refractive index of inner layer is larger than that of the outer layer. Analysis conclusion of the force trapping double-layer sphere provides reliable theoretical basis for this kind of sphere used as an optical handle.