Objective To study the levels of Matrix Metalloproteinase-3 (MMP-3) and interleukin (IL-1) in the synovial fluid and plasma of C57 black mice with osteoarthritis (OA) and their relationships with the severity of pathological changes so as to investigate their effects and correlation with OA. Methods The C57 black mice with OA were enrolled for this study. Different levels of exercise were appicated based on their age. Knee joint pathological changes were examined for pathological severity of OA. ELISA sandwich method was used to measure the levels of MMP-3 and IL-1 in serum and synovial fluid. Correlation analysis was performed to demonstrate the relationship between the levels of MMP-3 and IL-1 in the serum and synovial fluid, and the pathological severity of OA. Results ①Morphological observations: C57 black mice were characterized by spontaneously developing OA and the incidence and the severity of osteoarthritis gradually increased with age and exercising burdens. ② The level of MMP-3 and IL-1 in the synovial fluid of exercising mice MMP-3 (84±6) ng/ml, IL-1 (48±3) ng/ml was higher than that in the aged ones [MMP-3 (84±6) ng/ml, IL-1 (71±5) ng/ml J, the difference was significant (P<0.01). The level of MMP-3 and IL-1 level in the serum had a linear correlation with that of the synovial fluid. At the same time, they also had linear correlation with the pathological severity of OA (All r>0.67, and all P<0.01). Conclusion The levels of MMP-3 and IL-1 in serum and synovial fluid can help to make early diagnosis of OA, especially elevated MMP-3 level.