Abstract: Since surface crack propagation in pressure vessel often results in low cycle fatigue destruction,it is of significance to figure out low cycle fatigue surface crack propagation law.On the specimen with symmetrical double arcs,a semi-ellipse surface crack in the geometric center of the up-arc was machined and fatigue-prepared to simulate the character of pressure vessel with a surface crack.Simultaneously,in the arc side a knife-edge with a special shape and dimension for installing a COD displacement gage was designed to control the strain of surface crack front.With 10CrNiMo steel as an example,under cantilever bending loading mode,with a total six-grade strain range from small to big as the controlled parameters,the low cycle fatigue surface crack growth characteristics of the test material was investigated,which may provide a reference for assessing the remaining useful life of pressure vessels with surface cracks in it.