Lead antimony oxide nanoparticles (Pb1-xSbxO NPs) were synthesized by chemical precipitation and annealing treatments. The structural and optical properties of undoped and various Sb3+ -doped PbO NPs were investigated. The tetragonal phase of -PbO was found for both before and after various Sb3+ doping. The lattice parameters decreased for the 1.0 – 5.0 wt% Sb3+ doping, which indicated the increase of internal defects, but tends to an amorphization with exceeding 5.0 wt%. The overall band gap (Eg) values after Sb3+ doping (1.071.76 eV) are lower than undoped PbO (2.35 eV). These findings indicate a promising material for window layer fabrication and an absorber material for solar cell applications.