New cellulose acetate derivatives substituted with 6-(p-alkoxyphenyl)carbonyl-spirobenzopyran (COSP) were prepared from base-catalyzed etherification of cellulose acetate by S-(p-bromohexyloxyphenyl)carbonylspirobenzopyran The degree of COSP substitution was controlled by the feed amount of COSP and reached to max. 46 wt %. T-g of the resultant COSP bound cellulose (CA-COSP) was increased as the COSP substitution is increased. CA-COSP was soluble in aprotic polar solvents, to allow preparation of photochromic film by solution process. Reversible photochromic property was observed from the CA-COSP film by using two tight sources of UV and visible light.