The authors report the effect of superconductivity on the electronic transport and capacitance of La1.85Sr0.15CuO4/Nb doped SrTiO3 heterojunction. This heterojunction shows good rectifying property. With the occurrence of superconductivity, the capacitance, junction resistance, and diffusion voltage of the heterojunction show jumps, which correlate with the resistance change of La1.85Sr0.15CuO4. Analysis shows that the current-voltage behavior of the heterojunction is consistent with that of the inhomogeneous Schottky contacts. The results were discussed by considering the effect of superconductivity on the inhomogeneous heterojunction. This work is helpful for the understanding of superconductor based heterojunctions and inhomogeneous Schottky contacts.