Abstract: The paper studies the strength and toughness of 14mm 440MPa grade ship steel plate produced via TMCP.The microstructures of the steel are investigated by means of OM and TEM.The results show that low temperature toughness of the steel is excellent,with impact energy at-40℃ over 310J and transient temperature below 100℃.The good properties of 440MPa grade steel plate come from microstructure refining as low carbon,Nb-Ti micro alloyed treatment and TMCP technology.