In order to study the precipitation process and crystal structure evolution of copper precipitate in ferritic stainless steel, the growth process of copper precipitate was observed by atomic probe chromatography (APT) and high resolution transmission electron microscopy (HRTEM).As a result, the size of copper precipitate increases and the quantity density decreases with the prolonging of annealing time. And the shape of the precipitated phase changes from the initial spheroid to ellipsoid, and finally to rod. The growth curve can be fitted into a formula , which is consistent with Ostwald ripening rule. The orientation relationship between 9R structure and matrix is . The precipitation sequence of copper precipitate in the ultrapure ferritic stainless steel is bcc→9R→3R→ fcc.