The invention discloses a dyeing and finishing process for improving the color fastness to light of a light-colored fabric of an FDY (Fully Drawn Yarn) polyester filament yarn warp and weft four-way elastic textile. The dyeing and finishing process comprises a dyeing process; a formula of a dyeing auxiliary adopted in the dyeing process comprises the following components: 0.5g/L to 1g/L of high-efficiency dispersant, 2g/L to 3g/L of chelating dispersant, 0.3g/L to 0.5g/L of 99 percent glacial acetic acid, X percent (o.w.f.) (on Weight the Fabric) of disperse yellow AM-2R, Y percent (o.w.f.) of disperse red AM-SLR and Z percent (o.w.f.) of disperse blue AM-SLR, wherein the sum of X, Y and Z is not more than 0.5, and a bath ratio is 1: (3 to 4). According to the dyeing and finishing process, the light-colored fabric of the FDY polyester filament yarn warp and weft four-way elastic textile which does not contain a fluorescent whitening agent and is obtained by being dyed by a disperse dye with color fastness to high sunlight is used as greige cloth; the color fastness to light which is up to a rating of 5 to 6 is realized through the specific dyeing and finishing process.