Objective To study application of magnetic resonance imaging (MRI) in auxiliary diagnosis of anterior cruciate ligament injury. Methods 78 cases of anterior cruciate ligament injury treated in our hospital from September 2011 to September 2013 were selected, all patients underwent clinical examination and MRI examination, then underwent arthroscope operations research examination. Arthroscope operations research examination results were served as the gold standard, diagnosis of anterior cruciate ligament injury, accuracy, sensitivity and specificity by clinical examination and MRI examination were compared. Results True positive rate of clinical examination anterior cruciate ligament was 38.46%, which was significantly lower than MRI examination (66.67%) (P<0.05); false negative rate of clinical examination anterior cruciate ligament was 21.79%, which was significantly higher than MRI examination (2.56%) (P<0.05); accuracy of MRI examination was 94.87%, sensitivity was 66.67%, which were significantly higher than clinical examination (70.51%, 38.46%) (P<0.05). Conclusion MRI examination is a noninvasive, non radioactive diagnostic method with a higher accuracy, its inspection result can provide an important basis for arthroscopic examination and anterior cruciate ligament reconstruction, it has some clinical value in the diagnosis of cruciate ligament injury, should be applied and popularized.