Lead selenide (PbSe) thin films are widely used in the field of infrared detection due to their high infrared detection rate and sensitivity at room temperature. In recent years, PbSe thin films have been successfully grown on Si substrates. This article utilized the chemical bath deposition (CBD) method to prepare uniform and dense PbSe thin films on Si(100) substrates. The crystal structure, micro morphology, thickness, and energy band gap of polycrystalline PbSe thin films on Si(100) substrates were studied at a deposition temperature of 70 °C with a holding time of 30–120 min. Results showed that the prepared PbSe films bonded well with the Si(100) substrate. As the holding time increased, PbSe maintained [200] crystal orientation growth, and the crystallinity improved. The thickness of the PbSe thin film increased with the holding time, while the energy band gap first decreased and then increased. The PbSe thin film prepared with a holding time of 60 min had a thickness of about 388.5 nm, grew in the [200] crystal orientation, and had an energy band gap of 0.153 eV, showing the best optical properties.