A new copolymer was synthesized by free radical polymerization in solution from methyl 3α-methylacryloyl-7α,12α-dihydroxy-5β-cholan-24-oate (MACAME) and maleic anhydride (MAN). The copolymer was characterized by FTIR and functional group analysis. The reactivity ratios of the two monomers were estimated [rl = 11.6 (MACAME), r2 = 0.01(MAN)] by conducting a series of copolymerizations with a variety of monomer feed compositions and analyzing the copolymer composition. Thermogravimetric and differential scanning calorimetric analyses of the samples indicate that the copolymer possesses good thermal stability. The temperature at which the copolymer samples experienced a 10% weight loss (TWL) is over 287℃, and the Tg ranged from 174 to 185℃ for the copolymers.