The invention provides a metal alkoxide complex of Formula (I), wherein X, M, R1, R2, R3, m, n, y and z are as defined in the Description. The invention also provides a catalyst composition comprising the metal alkoxide complex and a hydroxy-containing compound, wherein the molar ratio of the metal alkoxide complex to the hydroxy-containing compound is 1:0.1-1000. The invention also provides a production method of poly-ε-caprolactone or polyactide, wherein an ε-caprolactone monomer or a lactide monomer is reacted in the presence of the metal alkoxide complex or catalyst composition to obtain poly-ε-caprolactone or polylactide. The metal alkoxide complex and the catalyst composition thereof can be used to catalyze the synthesis of poly-ε-caprolactone or polylactide with a high efficiency. The molecular weight of polycaprolactone or polylactide can be controlled by the molar ratio of the metal alkoxide complex and the hydroxy-containing compound, and is adjustable in the range of 1000-600,000, and wherein the molecular weight distribution is from 1.03 to 1.50. [Xn-mM(OCR1R2R3)m]y.(organic solvent)z   (I)