Glass forming technology is used to form channels of external electrode flat fluorescent lamps (FFL). The efficiency of FFL depends on the number and the length of the channels. Five FFLs with same size ($300;mm{ imes}80;mm$), different channel number, and different channel length were fabricated. The electrical and optical characteristics of 5 FFLs were evaluated. It was found that the FFL with one channel with its channel length of 1,110 mm and channel width of 7 mm corner width was shown to have the highest efficiency at room temperature operation.