Abstract: The stress intensity of Reactor Pressure Vessel local wall-thinning area is calculated in the edge stress field of nozzle by ANSYS-a FE software.And the stress concentration factor,the membrane stress intensity and the membrane stress plus the bending stress intensity vs the dimension and location of part-through slot have been discussed.In this article we generalized that the membrane stress intensity is in-tensifying by long half axis in an external convexity curve,intensifying by depth in a straight line,weakening by distance in an inner concave curve,and the membrane stress plus the bending stress intensity is no changing by long half axis nearly,intensifying by depth in a straight line,weakening by distance in an inner concave curve,and the stress concentration factor is minishing by long half axis in an inner concave curve,augmenting by depth in a straight line minishing by distance in an inner concave curve.