Electroplating was employed to prepare Cu film on the surface of Ni substrate. Deflection of Ni substrate with Cu film coating was measured in situ by a cantilever beam method. Based on the measured deflection, average internal stress and distributed internal stress in Cu film were calculated. The results show that average internal stress and distributed internal stress in the Cu film decrease abruptly with the thickness of Cu film increasing. Interfacial stress of Cu film is very large while growth stress is small. Average internal stress in Cu film, which is caused by the adjustment of the electron densities at both sides of the interface, was roughly calculated using the modified Thomas-Feimi-Dirac-Cheng (TFDC) electron theory. The calculated result of TFDC electron theory is close to that of the experiment, indicating that the calculation model of electron theory is of high accuracy