Using the Landau-Lifshitz equation, the propagating of spin wave in metallic magnetic stripe has been investigated, in which the effective boundary condition is applied for the dynamic magnetization of the metallic magnetic strip. The relationship between spin wave spectrum and width of the strip has analytically been derived. Numerical calculations show that in-plane confinement results in the obvious kinks in the threshold curves. And with the increase of strip width, the kink numbers almost rise exponentially, while the threshold jump at the first kink is nearly in inverse proportion to its width.