Research Objective: To discuss exercise performance and biochemical reactions of different load weight-bearing running of rats. Research Methods: 24 male 3-month-old SD rats were randomly divided into 3 groups (n = 8), namely, a none weight-bearing running group, a 35% maximum load weight-bearing running group, a 75% maximum load weight-bearing running group. After weight-bearing running training for 6 weeks, the maximum weight-bearing capacity, the blood lactic acid value and serum CK value of rats were tested and compared. Research Results: 30m/min speed running and 45m/min speed running respectively enabled the lactic acid value to generate first and second inflection points; weight-bearing running increased the serum CK-M value with the increase of bearing weight and load, and the blood lactic acid value and the serum CK value were significantly increased. Conclusion: 30m/min is the anaerobic threshold intensity of rat running; maximum load capacity of rats is about 65% of sole weight; weight-bearing running with appropriate load can not damage muscle fibers and can effectively mobilize II type muscle fiber, 75% maximum load weight-bearing running can mobilize II type muscle fiber to be fully raised, but can cause muscle fiber damage.