All-inorganic perovskite CsPbBr3 thin films have been prepared on Si (100) substrate by a pulsed-laser deposition (PLD) technique, and the morphology, structure, absorbance, and photoluminescence properties of CsPbBr3 thin films are investigated. A photodetector based on CsPbBr3/n-Si heterojunction has been fabricated, and the performances of the device are characterized. The heterojunction photodetector exhibits diode-like rectifying behavior, and the photocurrent-to-dark-current ratio and peak responsivity of the heterojunction are approximately 168.5 and 0.6 A/W (-5 V, 520 nm), respectively. Furthermore, the CsPbBr3/n-Si heterojunction photodetector exhibits fast response and recovery times. With good optoelectronic properties, CsPbBr3 thin films prepared by PLD should be widely applicable to high-performance photodetectors and other optoelectronic devices.