Abstract: The effect of different plastic deformation strain ageing on the performance of NVB ship plate steel has been studied which includes strength,ductility,low temperature toughness and brittle-ductile transition temperature.As a result,NVB ship plate steel is less sensitive to strain ageing,and after 5% aged,low temperature toughness of plateis is still good.By means of microstructure analysis,microstructure and shear fracture morphology at different temperature are discussed.The results show,banded structure worsen toughness, nonmetallic inclusions has negative for brittle-ductile transition temperature.This article also expatiate strain ageing mechanism in dislocation aspect.