Fluorescent brightener 4,4′-bis(2-sulfostryl)biphenyl disodium salt (CBS) was synthesized by using 4-chlorobenzyl chloride, trimethyl phosphite and benzaldehyde-2-sulfonic acid sodium salt as starting materials through three-step reaction. The chemical structure was characterized by means of IR and NMR. The photoinduced isomerization phenomena and fluorescence emission properties were studied. In addition, the effects of concentration, pH and light irradiation time on fluorescence properties were investigated. The whiteness measurement was performed through dyeing filter paper and cotton. The optimized reaction conditions were as follows: reaction temperature for sodium 2-(4-chlorostyry)benzenesulfonate synthesis was 45℃, n(4-chlorobenzyl chloride):n(sodium methoxide) = 1.0:1.1, reaction temperature for CBS synthesis was 80℃, m(catalyst):m(sodium 2-(4-chlorostyry) benzenesulfonate) = 0.04 and n(NiCl2):n(PPh3):n(Zn) = 1:3:2. The results show that the overall yield of CBS was 66.7%. With the increasing of light irradiation time, trans-isomers transformed to cis-isomers, fluorescence intensity reduced. The fluorescence intensity of CBS under alkaline condition was higher than that of acidic condition. The quenche mass concentration of CBS was 10 mg/L.