A multi-level spectral Galerkin method for the two-dimensional nonstationary Navier-Stokes equations is presented. The method proposed here is a multiscale method in which the fully nonlinear Navier-Stokes equations are solved only on a low-dimensional space Hm1; subsequent approximations are generated on a succession of higher-dimensional spaces Hmj, j=2, . . . , J, by solving a linearized Navier-Stokes problem around the solution on the previous level. Error estimates depending on the kinematic viscosity 0<ν<1 are also presented for the J -level spectral Galerkin method. The optimal accuracy is achieved when mj=O (m 3/2 j−1), j=2, . . . , J. We demonstrate theoretically that the J-level spectral Galerkin method is much more efficient than the standard onelevel spectral Galerkin method on the highest-dimensional space HmJ .