mono-trimethylolpropane trimaleate(MTPTM) was prepared by esterification from trimethylolpropane(TMP) and maleic anhydride(MA). MTPTM was employed as allyl branching monomer to copolymerize with methacrylic acid to prepare hyperbranched copolymers(HBCs). The structure of MTPTM was characterized by 1H NMR and 13C NMR. The effects of feed ratio on HBCs properties including molecular weight and its distribution, aqueous solution viscosity, thermal stability and glass transition temperature were investigated. The results indicated: with n(MTPTM)/n(MAA) increasing from 1:3 to 1:15, HBCs molecular weight and its distribution showed a minimum(Mw=2.09×104，Mw/Mn=1.66) for n(MTPTM)/n(MAA)=1:9, aqueous solution viscosity manifested the same trend with a minimum at n(MTPTM)/n(MAA)=1:6, glass transition temperatures, however, showed an reverse trend with a maximum (Tg=274.5℃)for n(MTPTM)/n(MAA)=1:9. Increasing of MAA molar ratio was helpful to the enhancement of HBCs thermal stability.