Abstract: The effects of interpass temperature and weld passes on the microstructure and toughness of deposited metals by self-shielded flux cored wires were investigated in the paper. The results indicated that with the increase of interpass temperature,the pro-eutectoid ferrite amount increases,the austenite amount increases first and then transforms into carbide in martensite austenite island,which results in the impact toughness increasing firstly and then decreasing. The toughness of deposited metals is increased with the increase of welding layer,which attributes to the reduction of size and content of martensite austenite island as well as the increase of ratio of fine grain zone.