Objective To compare the MRI, CT and X-ray in the diagnosis of multiple myeloma (MM). Methods A total of 80 cases of MM who were admitted to the hospital from January 2017 to January 2018 were selected and given MRI, CT, and X-ray examinations. The imaging features and the diagnostic efficacy of MRI, CT and X-ray were analyzed. The detection rates of bone lesions in different sites were recorded by MRI, CT and X-ray. Results Among 80 patients, the most common type of lesion is bone destruction in X-ray, accounting for 80%. In CT examination, the most common lesion was bone destruction, accounting for 87.50%. In MRI, the most common lesion type was multifocal type, accounting for 52.50%. The accuracy and sensitivity of MRI diagnosis were higher than those of CT and X-ray(P<0.05). There was no statistical significance in the specificity of MRI, CT and X-ray (P>0.05). The detection rate of skull lesions by MRI was higher than that by CT and X-ray (P<0.05). There was no significant difference in the detection rates of lesions in spine, pelvis, ribs and extremities by MRI, CT and X-ray (P>0.05). Conclusion The accuracy and sensitivity of MRI for MM diagnosis are higher than those of CT and X-ray, and MRI is more advantageous in the examination of lesions in skull.