Objective To study the CT signs features in elderly patients with type 2 diabetes mellitus (T2DM) complicated with pulmonary tuberculosis (PTB) so as to provide reference for improving clinical diagnosis and treatment. Methods Each 80 cases of patients with T2DM and PTB (observation group) and patients with simple PTB (control group) from August 2016 to August 2018 in our hospital were selected for the study and they were given CT examination. The image features of lesion location, involvement range and lesion morphology and nature were compared between the two groups. Results There was no significant difference in the lesion location between the two groups (P>0.05), and the double lung involvement rate and average number of affected lung segments in observation group were higher than those in control group (P<0.05). The proportion of nodular lesions in observation group was less than that in control group, and the incidence rates of cavitation, patchy shadows, pleural effusion and lymphadenopathy and the cavitation quantity were higher than those in control group(P<0.05). Conclusion CT signs of elderly patients with T2DM complicated with PTB are significantly different from those of patients with PTB. Except for a wider involvement range, there are more changes in the lesions morphology whose main manifestations are multi-lobes or large consolidation of lung segments, accompanied by exudation, caseation, cavitation formation and tree-inbud sign and greatly reduced nodular lesions.