We studied spin waves excited by two or more excitation sources in a uniform nanostripe waveguide without periodic structures. Several distinct spectrum gaps formed by spin waves interference rather than by Bragg reflection were observed. We found the center frequency and the number of spectrum gaps of spin waves can be controlled by modulating the distance, number and width of the excitation sources. The results obtained by micromagnetic simulations agree well with that of analytical calculations. Our work therefore paves a new way to control the spectrum gaps of spin waves, which is promising for future spin wave-based devices.