Nano-indentation studies using atomic force microscopy (AFM) were introduced to investigate the effects of hydrolysis degradation on mechanical properties of polyglactin 910 monofilament sutures. The polyglactin 910 sutures were immersed in phosphate buffered saline (PBS) solution of pH 5, 7.4, 10 without enzyme and pH 7.4 with esterase enzyme. After that, the samples were incubated at 37 oC under an oscillation of 80 rpm. Samples were removed for testing after 7, 14, 21 and 28 days. The effects of degradation on gradation of Young’s modulus values across fiber cross-section were studied by doing progressive nano-indentation from center to surface of cross section of the sutures. Results indicate that the pH 7.4 condition hydrolysis degradation did not have a significant impact on variation of Young’s modulus values of the polyglactin 910 sutures from the center to the surface after different degradation times. And the Young’s modulus from the original samples to sutures after 4 weeks degradation have a decreasing trend, but not including the first week. Then the SEM, FTIR and Tensile test were conducted to investigate the mechanical and chemical properties of polyglactin 910 monofilament sutures.