The hyperbranched styrene-maleic anhydride polymers were modified with alcohol, and a series of modification conditions, such as reaction temperature, time, types and dosages of alcohol, were investigated in detail. Aimed at the dispersity for red P.R122, Esters of hyperbranched styrene-maleic anhydride copolymer M-BPSME were preparated on the basis of optimizing conditions. M-BPSME has been characterized by FTIR spectra, and has higher esterification degree when reactive time is 6h and temperature 80oC. Besides, the dispersing ability of LPSMA, BPSMA and M-BPSME to red P.R122 was as follows: M-BPSME > BPSMA > LPSMA. Interesting, BPSME showed high dispersity to red P.R122, that centrifugal and heat stabilities were over 97%.