In order to improve the adverse effects on the precast pavement structure caused by cavities under slabs and joint load transfer efficiency decline, the post-tensioned prestressed steel stranded joint (PJ) and combined joint (ZJ) are proposed, and the full-scale simulation model is established by ABAQUS. Based on the similarity theory and 3D printing technology, the indoor scale model is established and the simulation model is verified. Then, the optimal local size of PJ is recommended, the mechanical response and the influence by cavities under slabs with PJ, ZJ and common joints are compared, the sensitivity of factors affecting slab mechanical response when there have cavities is analyzed for new joint. The results show that the load transfer efficiency of ZJ can reach 84% and the flexural-tensile stress of ZJ slab can be reduced by 50% when 6 prestressed tendons with diameter of 15.2 mm are laid. Compared with common joints, the flexural-tensile stress of ZJ slab is almost unaffected by cavities, and the load transfer efficiency of ZJ decreases by only 1% when the cavity size grows from 0 m to 0.2 m. Therefore, the new joint proposed in this paper can not only meet the requirements of joint load transfer, but also significantly reduce the adverse effects of cavities on slab flexural-tensile stress and joint load transfer efficiency.