Objective: To evaluate the clinical application effect of 3.0T magnetic resonance 3D proton density weighted imaging (3D-PDWI) + CT-like imaging in the grading imaging diagnosis of knee cruciate ligament injury. Methods: The clinical data of 60 patients with knee cruciate ligament injury admitted to People’ s Hospital of Ruijin City from September 2023 to December 2024 were retrospectively analyzed. All patients received 3.0T magnetic resonance conventional scan, 3D-PDWI, CT-like imaging and arthroscopy. With arthroscopy as the diagnostic gold standard, the accuracy rates of the above imaging examinations in the diagnosis of knee cruciate ligament injury grading were observed. Results: Among 60 patients with knee cruciate ligament injury confirmed by arthroscopy, there were 35 cases of partial ligament injury and 25 cases of complete injury. The sensitivity, specificity, accuracy and Kappa value in the diagnosis of knee cruciate partial ligament injury were 91.42%, 84.00%, 88.33% and 0.758 of 3.0T magnetic resonance 3D-PDWI + CT-like imaging respectively. Conclusion: 3.0 T magnetic resonance 3D-PDWI + CT-like imaging has high accuracy rate in the diagnosis of knee cruciate ligament injury grading, and it can provide accurate imaging reference for the choice of treatment method.