This paper indicated a theoretical model for describing the effects of the interface recombination on the heterojunction solar cell parameters based on single wall carbon nanotube and GaAs as p-n junction. By choosing the zigzag nanotube and GaAs layer, it is shown that by increasing the interface recombination, short circuit current and open circuit voltage decrease. Depletion current, J-V characteristic and ideality factor variation in terms of interface recombination have been calculated.