The calculation of critical temperature for Nb-Cu multilayer film superconductor without any adjustable parameter shows that as the periodic character of multilayer film is considered, the theory of proximity effect agrees reasonably with experiment within the range of layer thickness d>30?.It is also shown that there exists damped oscillation in the dependence of critical temperature Tcns on d, the electronic structure of interface between Nb and Cu has obvious influence upon Tcns only when d<30? and the strong heterogeneous interface probably increases the (NV) of Nb.