Abstract: Objective To study the relationship between myofibril fragmentation index （MFI） of human skeletal muscle and postmortem interval （PMI）. Methods The protein concentrations of human right biceps brachii muscle and right quadriceps femoris muscle were obtained at different PMI, and detected at room temperature by biuret method. The MFI of skeletal muscle at 540 nm was measured by ultraviolet spectrophotometer. Regression analysis was performed with time of death as independent variable （x） and MFI as dependent variable （y）. Results In early PMI, the MFI of human skeletal muscle increased obviously according to the prolongation of PMI, and peaking by 12 h and then tended to steady. Within 12 h after death, the regression equations of right biceps brachii muscle and right quadriceps femoris muscle were y=32.660+3.227 x（r=0.987 9） and y=32.380+3.495 x（r=0.983 9）, respectively. Conclusion There’s high correlation between MFI and PMI. Combining with forensic practice, MFI can be used for the estimation of early PMI （especially in 12 h）.

Key words: forensic pathology, muscle, skeletal, myofibril fragmentation index, postmortem interval