A double parallel junctions (DPJ) silicon solar cell structure is designed. The solar cell forms a PN junction and a NP junction in the same monocrystalline silicon solar cell, respectively, which absorbs short wave energy and long wave energy. The two junctions share a N-type region and form a parallel structure by the N-type region. The short circuit current of the solar cells is increased about 11.9% compared with the traditional monocrystalline silicon solar cells, and the open circuit voltage of the solar cells keeps constant. The optimal technological condition of DPJ solar cells is studied, and the results show that the spectrum response of the solar cells enhances firstly, and then decreases with the increasing of diffusion concentration for deep junction and shallow junction. The spectrum response of the solar cells increases firstly, then remains unchanged with the redistribution diffusion temperature raising and the diffusion time extending of the impurities after the diffusion of deep junction is completed. The spectrum response of the solar cells increases slightly with the increase of shallow junction diffusion time and temperature.