A method of preparing degradable and environment responsive composite microgels, belonging to polymer material synthesis and biomaterial technology fields. Firstly, a copolymer of L-malic acid and 6-hydroxyhexanoate is prepared; then, N,N,N′,N′-tetramethyl cystamine is prepared. The copolymer and N,N,N′,N′-tetramethyl cystamine are mixed in an organic solvent to form a mixed solution which is added into excess distilled water to produce composite microgels. The microgels have advantages of mild preparing conditions, fast reaction speed without catalysts, no impurity remained, and controllable degradation rate. The microgels can load anticancer drug doxorubicin hydrochloride, showing environment responsive controlled release due to introduction of carboxyl groups and disulfide bonds.