Comprehensive data, including weather pattern, Doppler radar, AWS on a gust fron t occurred on May 6,2007 were analyzed and compared with the squall line on June 10,2006 and a gale process on June 28,2007. Results show that generation mechan ism of a narrowband echo accompanying gale wind is of abrupt refractive index changes along the interface between warm and cold air masses, which lead to elec tromagnetic wave scattering and reflecting, and in turn forms weak echo. Another important factor is the sinking and diffusing motion of cold air in upper level . Behind the narrowband echo, there probably is no main echo following. The fr ont of inclining downdraft is unfavorable to the narrowband echo.