Objective To study the diagnostic values of 3.0T magnetic resonance imaging (MRI) routine sequence combined with diffusion-weighted imaging (DWI) in preoperative T and N stages of lung cancer and its correlation with pathology. Methods A total of 71 cases of patients with lung cancer treated in our hospital from August 2015 to July 2017 were selected and were given 3.0T MRI routine sequence combined with DWI examination. The postoperative pathological results were taken as criterion, and the preoperative T and N stages results of 3.0T MRI combined with DWI and its correlation with pathological findings were analyzed. Results The total accuracy of preoperative T stage in 71 patients was 92.96% by 3.0T MRI combined with DWI scan. The sensitivity, specificity and accuracy were 80.00%, 100.00% and 98.59% respectively at T1-2 stage, and were 87.50%, 94.55% and 92.96% respectively at T3 stage and were 96.00%, 90.48% and 94.37% at T4 stage. The results of consistency test diagnosis with pathology showed κ=1.416 (P>0.05). The total accuracy of preoperative N stage in 71 patients was 91.55% by 3.0T MRI combined with DWI scan. The sensitivity, specificity and accuracy were 94.74%, 96.97% and 95.77% at N0 stage, and were 89.47%, 92.31% and 91.55% at N1 stage and were 85.71%, 98.25% and 95.77% at N2-3 stage. The results of consistency test diagnosis with pathology showed κ=0.748 (P>0.05). Conclusion 3.0T MRI routine sequence combined with DWI can be used as important method for preoperative T and N stages of lung cancer diagnosis, and the consistency is high with pathological results.