Crystal structure and photoelectric properties of the light absorbing layer (CsPbI3)/electron transporting layer (SnO2) heterogeneous interface were studied at the atomic and electronic levels by using the first principles calculations. The calculation of electronic band structure indicates that band gap of the cubic CsPbI3 is about 1.48 eV. The lattice mismatch of SnO2 (110)/CsPbI3 (100) interface is 4.45 % and the interface binding energy is -2.86 J/m(2). Due to the contribution of I-5p, Pb-6p, Pb-6s, and O-2p orbitals with the CsPbI3 (100) layer1 and SnO2 (110) layer1, the SnO2 (110)/CsPbI3 (100) interface exhibits some new electronic density of states nearby the Fermi level. The static dielectric constant of crystal CsPbI3 is 6.22, and its optical band gap is also approximate 1.48 eV.