Objective To investigate the role of magnetic resonance imaging (MRI) T2 mapping imaging in evaluating the condition of knee osteoarthritis (OA). Methods 70 cases of OA patients treated in our hospital from January 2017 to February 2018 were selected, including 21 cases of mild OA, 30 cases of moderate OA, 19 cases of severe OA, and 60 healthy volunteers as the control group, MRI T2 mapping imaging was given. Results The T2 value of the knee joint cartilage in the OA subgroups were significantly higher than that in the control group (P<0.05), and the T2 value of the severe OA group was (44.03±5.10) ms, which were significantly higher than that in the mild OA group and the moderate OA group (P<0.05). According to the pathological grading of Collins, there were 15 cases of grade 0-I, 32 cases of grade II-III, and 13 cases of grade IV lesions; The T2 value of grade IV lesions was (50.24±3.96) ms, which were significantly higher than that of grade 0 to grade I and grade II to III (P<0.05). The T2 value was positively correlated with the severity and Collins classification (rs=0.516 and 0.560, P<0.05). Conclusion MRI T2 mapping imaging quantitative analysis of cartilage can reflect the severity and pathological grading of OA patients, which is helpful for monitoring and diagnosis of cartilage injury in knee joint.