Abstract: Objective To study the changes of mitochondrial morphology and mitochondrial membrane potential following acute spinal cord injury（SCI）. Methods Thirty-six SD rats were randomly divided into control group（sham operation group） and SCI group. Each group was divided into 4 h group, 8 h group and 16 h group after treatment（6 in each group）. The SCI group was established using Allen’s method. Spinal cord of rats in control group was exposed. Changes of mitochondrial morphology were observed under TEM and mitochondrial membrane potential was measured using JC-1. Results The mitochondrial volume was larger with its crest deranged in SCI group 4 h after SCI. The mitochondrial volume was larger with its crest swollen in 8 h group. The mitochondrial structure was unclear with its crest broken and deranged, and some membrane ruptured and vacuole formed in 16 h group. The mitochondrial membrane potential was significantly lower in SCI group than in control group 4, 8 and 16 after SCI（P＜0.01）. Conclusion Significant change occurs in mitochondrial morphology and structure of rats with their mitochondrial membrane potential significantly decreases after SCI.