Abstract: Objective :To evaluate diagnostic value of MR imaging detecting nasopharyngeal carcinoma (NPC) involved basicranial bone. Methods : Reviewed and analyzed MRI material of 350 cases NPC at first visited, detected basicranial bone erosion in 196 cases. All cases were proved to the NPC by pathology. The main pathologic type is squama carcinoma, There were 180 squama carcinoma in 196 cases. The MR images of 134 patients with NPC were obtained on O.ST unit, 62 patients on 1.5T unit. The head coil was used. Only unenhanced scan was in 8 case of 196 cases. There were 188 cases with enhanced scan by intravenous injection Gd-DTPA (O.lmmol/kg) after unenhanced scan. Results :In 196 cases with NPC involved basicranial bone,there were 178 cases (90.81%) in unilateral basicranial bone erosion, 18 cases (9.19%) in bilateral basicranial bone erosion. There were 65 cases with singlesite involved and 131 cases with muti-sites involved. Total involved sites were 698 sites. The patterns and frequencies of bone erosion were as follows: osteosclerosis 13 sites (1.86%), osteolysis 565 site(80.95%), marrow erosion 120 sites (17.19%). Conclusions :MR imaging is a preferred method in evaluating nasopharyngeal carcinoma invasion basicranial bone. MR imaging is more sensitive than CT especially in detecting NPC invasion marrow.