BiScO3-PbTiO3 (BSPT) thin films were fabricated via a sol-gel method on Pt(111)/Ti/SiO2/Si(111) substrates. The effects of different factors on the orientation of the sol-gel-derived BSPT thin films were investigated. The results showed that a higher lead excess concentration, longer drying time, higher pyrolysis temperature, longer pyrolysis time, higher crystallization temperature, and longer crystallization time could enhance the (100) orientation of the BSPT thin films. Based on the experimental results, a mechanism for the orientation evolution in the sol-gel-derived BSPT thin films was proposed. The production of the (100) orientation was attributed to the (100)-oriented PbO nanocrystals forming during the pyrolysis process due to the lattice match.