Abstract: Objective: To explore the application of energy spectrum purification combined with iterative reconstruction algorithm in low-dose CT examination of patients with secondary pulmonary tuberculosis. Methods: 70 patients with secondary pulmonary tuberculosis diagnosed in Wuhan Pulmonary Hospital from April to June 2019 were selected as the research subjects. We performed initial detection on group of conventional dose: tube voltage of 110 kV, reference tube current 52 mAs, FBP image reconstruction; then we performed reinspection on the low-dose group (spectral filtration): tube voltage Sn of 110 kV, reference tube current of 73 mAs, SAFIRE level 3 image reconstruction. Subjective image score, CT value of ascending aorta, image noise, SNR and radiation dose were compared between the two groups. Results: There was no statistically significant difference in subjective scores between the two groups, which met the requirements of clinical diagnosis. there was no significant difference in CT value between the two groups; image SNR of the low-dose group was lower than that of the conventional dose group; the ED (0.36±0.15) mSv in the low dose group was 84.7% lower than that in the conventional dose group (2.35±0.73) mSv. Conclusion: Energy spectrum purification combined with iterative reconstruction algorithm can significantly reduce the radiation dose applied in patients with secondary pulmonary tuberculosis while the image quality can meet the requirements of clinical diagnosis.