The effects of molar ratios and sintering times on crystal structures and surface morphology on NdFeO 3 oxide alloy have been studied. NdFeO 3 oxide alloy formed by chemical preparation with solid reaction method using raw oxide Fe 2 O 3 (99.9%) and Nd 2 O 3 (99.9%) powders. In this article we reported the effects of molar ratios x=(–0.1,–0.2 and–0.3) and sintering times for 15 h and 20 h on crystal structures and surface morphology of Nd 1+ x FeO 3 synthesized by solid-state reaction method. The results indicate that variation of molar ratio and sintering time has influenced the FWHM, crystalline size and grain size. The Nd 1+ x FeO 3 have a major phase is NdFeO 3, and other minor phases are Fe 2 O 3, Nd 2 O 3 and Nd (OH) 3. The dominant intensity of hkl (121) with a value in FWHM, crystallite size, and grain size an indication the results will be applied as a gas sensor material as the focus of the further study.