Abstract: The effect of Nb on the microstructure and mechanical properties of low-alloy wear-resistant steel was analyzed by optical microscopy,scanning electron microscopy,transmission electron microscopy and mechanical property test. By adding 0.034% Nb in low-alloy wear-resistant steel,the hardness increases by HB 9,the Charpy impact energy soars to 37.6J from 29.4J at -20℃ and the anti-wear performance improves by 3.5%. Microstructure refinement and precipitation strengthening are main reasons for the improvement of hardness and impact toughness. Nano-sized particles of Nb C in the Nb-bearing steel precipitate in the process of austenization,pin the austenite grain boundaries and inhibit the growth of austenite grains. This pining type is in accordance with the Zener model,but different from precedent research.