<正> An additional lower hybrid wave (LHW) with a higher refractive index (N∥) wasinvestigated in the HT-7 tokamak to bridge the spectral gap. It was found that the spectralgap between the wave and the electrons in the outer region was bridged by the additional wavewith a higher N∥ spectrum. The results showed that the sawteeth oscillation was suppressed bylaunching the additional wave, and that the power deposition profile was moved outwards and thecurrent profile was broadened due to the application of the additional wave. Our study indicatesthat the spectral gap may be bridged by an additional wave with a higher N∥ spectrum in theouter region.