Monoclinic raspite PbWO4 nanobelts were synthesized at 30°C via the precipitation reaction of Na2WO4 and Pb(NO3)2 in aqueous solution without any additives. The starting molar ratio (r) and the aging time were found to play crucial roles in the phase control of PbWO4 crystals. Tetragonal stolzite PbWO4 nanoparticles were formed at r ≤ 1, whereas monoclinic raspite PbWO4 nanobelts were obtained at r > 1. The formation mechanism of raspite PbWO4 nanobelts was explored in detail by monitoring the morphology and structure evolution via SEM, XRD, and Raman measurements. It was found that monoclinic raspite PbWO4 nanobelts were formed through a phase transformation of tetragonal stolzite PbWO4 nanoparticles and a subsequent oriented growth in the aging process. In addition, the photoluminescence properties of these two kinds of PbWO4 were studied.