Objective To investigate the value of MR arthrography (MRA) in the diagnosis of partial tear of rotator cuff. Methods A retrospectively analysis was made to MRA and MRI performance of 79 cases with partial tear of rotator cuff, and contrasted it with the results of arthroscopy. Results For all 79 cases with partial tear of rotator cuff, the diagnostic sensitivity, specificity and accuracy of MRI were respectively 94.74％,76.12％ and 95.18％. MRA could only clearly show 32 cases with the inner layer (articular surface) tear of rotator cuff, and the sensitivity, specificity and accuracy were respectively 96.88％,100％ and 98.73％, which were obviously higher than conventional MRI. Compared with arthroscopy, the diagnostic results showed excellent consistency(Kappa=0.970), and the difference had statistical significance(P＜0.05). However, MRA wasn't able to show the outer layer (slippery bursa) and the intermediate layer (tendon) tear of rotator cuff. Conclusion MRA, an effective complement of MRI in the diagnosis of partial tear of rotator cuff, can accurately determine the scope and degree of the inner layer tear of rotator cuff, and it can provide more accurate basis for clinical diagnosis and treatment. However, for the outer layer and the intermediate layer tear of rotator cuff, MRA are not able to diagnose and show the damage the location and degree