Abstract: In this paper the effects of microalloying element Nb and Ti on the microstructure and toughness of submerged melt welding joint of continuous casting 10MnNiCr steel are studied by means of optical microscope and through impact test.The results show that the impact toughness of welding metal and heat affected zone of Nb-V-Ti microalloyed steel is higher than that of Nb-V microalloyed steel. The side plate ferrite promoted easily by element of Nb is disadvantageous of toughness. The element of Ti affects the toughness of submerged melt welding joint abviously for it helps forming acicular ferrite in the welding metal and prohibiting the coarsening of CG-HAZ grain.