BACKGROUND:We built Sprague-Dawley rat models with mild, moderate, and severe spinal cord injuries to accord with the spinal cord injury types for basic empirical study, and consequently to further understand the microenvironmental change in Sprague-Dawley rats with spinal cord injury, and to provide help for clinical treatment. OBJECTIVE:To observe the changes in nerve function, pathological manifestation and motor sensory evoked potential in Alen’s models and Sprague-Dawley rats with complete spinal cord transection at different time points after spinal cord injury by simulating the microenviroment in Sprague-Dawley rats. METHODS: A total of 125 healthy adult female Sprague-Dawley rats were selected and randomly divided into group sham operation group, 100 gcf hit potential group (20 g×5 cm), 200 gcf hit potential (20 g×10 cm), 300 gcf hit potential group (20 g×15 cm), and spinal cord complete transection group with 25 rats in each group. At 1, 5, 7, 14 and 28 days after model establishment, the degree of spinal cord injury was identified by the BBB scores of motion function, motor evoked potential, and pathological section. RESULTS AND CONCLUSION:(1) Totaly 24 Sprague-Dawley rats died in the experiment. The death rate and the rate of complications were highest in the spinal cord complete transection group. The BBB score of each group was decreased. The BBB scores in every group increased as time went on. There were significant differences between each surgery group and the sham operation group at corresponding time points (P < 0.05). No significant difference was found between the 300 gcf hit potential group and the spinal cord complete transection group at corresponding time points (P > 0.05). (2) In each surgery group, the infiltration of inflammatory cels and obvious sweling of neurons were visible at 1 day after injury. Neural cels reduced with time prolonged. At 28 days after injury, a large number of astrocytes proliferated, scar and spinal cord cavity formed. Above symptoms were worse in the 300 gcf hit potential group and spinal cord complete transection group than in the 100 gcf and 200 gcf hit potential groups. (3) Significant differences in amplitude and latency were detectable between each surgery group and the sham operation group (P < 0.05). No significant difference in amplitude and latency was detected between the 300 gcf hit potential group and the spinal cord complete transection group at corresponding time points (P > 0.05). Results confirmed that hit potential of 20 g×5 cm, 20 g×10 cm and 20 g×15 cm can simulate the microenvironment of Sprague-Dawley rats with mild, moderate and severe spinal cord injury. The rate of complication was lower in modified Alen’s model of different hit potentials than in models of spinal cord complete transection, and was more accorded with basic research.