Nano-crystalline PbSnO3 was synthesized by a sol-gel route. It was an anion-deficient pyrochlore (a = b = c = 1.0677 nm) with space group Fd3m. TEM images confirmed the nano-size of particles as similar to10 nm, aggregated into larger clusters up to I mum. DSC-TGA investigation revealed that the PbSnO3 was unstable >800degreesC with 2.95% weight loss. The products of the reactions, Pb2SnO4 and SnO2, were identified by in situ high-temperature XRD. The complex decomposition reactions were deduced as (2 + x)PbSnO3 = Pb2SnO4 + (1 + x)SnO2 + xPbO (x = 0.104). The lattice parameters of PbSnO3 were determined by high-temperature XRD. The cell volume of PbSnO3 increased with increasing temperatures. The average volumetric thermal expansion of PbSnO3 was calculated as (beta = 3.35 x 10(-5)/degreesC).