Residual stress in aluminum alloy affects the mechanical performance of the material. The effective evaluation of residual stress state (RSS) including the directions and values of principal stresses is of great concern. This article attempts to test RSS in aluminum alloy by eddy current (EC) method, which has characteristics of nondestructive, noncontact, and reliable. The approach involves solving forward problem and inverse problem. The forward problem is to establish relation between EC responses and stress state in terms of EC response surfaces and the inverse problem is to determine RSS with measured EC signals based on the EC response surfaces. A two-dimensional scan is performed and the image of equivalent residual stresses is displayed to indicate the distribution of residual stress. Finally, blind-hole testing is conducted to validate the proposed method.