Abstract: Poly(lactic acid-co-glutamic acid) (PGLA), a biodegradable and pHsensitive hyperbranched polymer, was synthesized by heating L-glutamic acid (Glu), D，L-lactic acid and pyromellitic dianhydride with the present of stannous chloride.1H-NMR spectrum results show that the unique branched architecture comprising of the PLA and branched polyglutamic acid unit, without glutarimide unit. Copolymer has good pH sensitivity and is soluble in aqueous solution of sodium hydroxide (pH≥7.4). The volume of colloidal particles forming in aqueous solution is maximum at about pH=9.