Objective To investigate and compare the application value of multi-slice spiral CT (MSCT) and magnetic resonance (MR) in the diagnosis of knee joint cruciate ligament injuries. Methods 56 patients with closed knee joint injury who were treated in the department of orthopaedics in our hospital were selected as the research objects. 16 slice spiral CT (MSCT) and magnetic resonance (MR) scanning were performed and the results were compared with those of arthroscopy. Results The PCL angle, CT value of PCL, AT angle and CT value of ACL of the injured limbs on oblique sagittal images of MSCT and MPR were significantly lower than those of the uninjured extremity (P＜0.05); The diagnostic results of arthroscopy were taken as the golden standard, the diagnostic accuracy of MSCT was 95.24% while of MR was 98.41% (P＞0.05). The imaging findings of MSCT showed obvious thickening and swelling of cruciate ligament, density decreasing, blurred peripheral fat spaces, clear edges or without clear edges; Avulsion fractures showed high-density free fracture flats attached to the ligament and part presence of contracture of the ligament. The imaging findings of MR showed obvious thickening of ligament. T1 and T2 showed irregular high or slightly high signal and avulsion fracture showed low signal on T1. Ligament relaxation is wavy; T2 showed irregular high signal and some obvious bone tissue separation signs. Conclusion The results of MSCT scan for knee joint cruciate ligament injuries are basically consistent with those of MR, which can be taken an preferred imaging method for the diagnosis of such diseases.