The invention relates to a modification method for a SnO2 electron selective transmission layer. The modification method comprises steps of (1) doping agent that is inorganic acid, sulfonic acid, amino acid or sulfur-containing ammonium salt, and doping concentration of 0.1-10at%; (2) preparation of a precursor solution: adding a required doping agent to prepared SnO2 sol with concentration of 1-5wt% according to the doping concentration, ultrasonic oscillating for 30-60 minutes at 30-80W to fully mix and uniformly disperse the doping agent; (3) preparation of a film: cleaning ITO glass, thentreating the ITO glass with UV ozone, and then spin-coating the prepared doping SnO2 sol on the surface of the ITO glass; and (4) film annealing. The modification method for the SnO2 electron selective transmission layer has the beneficial effects of improving SnO2 carrier migration rate and electronic extraction capability, lowering energy level mismatch of SnO2 and a perovskite layer, improvingoptical transmittance of a SnO2 film, improving crystalizing quality and stability of the perovskite layer, and improving short circuit current density, open-circuit voltage, fill factor and efficiency of a perovskite battery.