Thin¯lm of tin oxide (SnO 2 ) was prepared on p-type polished silicon wafer by ultrasonic spray pyrolysis technique using SnCl 4 precursor solution to fabricate nanospherical n-SnO 2 /p-Si heterojunction photoelectric device. Deposition of¯lm was achieved at 400 C substrate temperature. The self-made ultrasonic spray pyrolysis system is very cheap and convenient. The microstructural, optical and electrical properties of the SnO 2¯l m were characterized by XRD, SEM, XPS, UV-VIS spectrophotometer, four point probe and Hall e®ect measurement, respectively. The SnO 2 lm has the nanospherical particles. The electrical properties of heterojunction were investigated by I-V measurement, which reveals that the heterojunction shows strong rectifying behavior under a dark condition. The ideality factor and the saturation current density of this diode are 4.27 and 2:52 Â 10 À6 A/cm 2 , respectively. And the values of I F =I R (I F and I R stand for forward and reverse current, respectively) at 5 V is found to be as high as 248. The SnO 2 /p-Si heterojunction device exhibits obvious photovoltaic e®ect. Under an AM1.5 illumination condition, the open-circuit voltage (V oc ), short-circuit current density (J SC ),¯ll factor (FF) of the device are 150 mV, 3:9 Â 10 À3 mA/cm 2 and 20.58%, respectively. High photocurrent is obtained under a reverse bias when the crystalline quality of SnO 2¯l m is good enough to transmit the light into p-Si. Under 6.3 mW/cm 2 illumination, when the reverse bias is À5 V, the photocurrent gain is as high as 86.