Abstract Reducing the radiation dose and maintaining treatment efficacy during microwave ablation (MWA) of lung tumors is of great importance. The objective of this study is to evaluate the feasibility of using spectral shaping technology (100Sn kV) to reduce radiation dose in CT-guided lung tumor MWA. Here, we conducted a prospective, randomized, double-blind and non-inferiority trial including 114 patients diagnosed with lung malignancy who were scheduled for CT-guided lung tumor MWA. The patients were randomly divided into two groups: the experimental group (n = 57), which received spectral shaping protocol CT-guided lung tumor MWA (with scanning voltage of Sn100 kV and reference current of 96 mAs), and the control group (n = 57), which underwent the standard-dose protocol CT-guided lung tumor MWA (scanning voltage of 120 kV and reference current of 94 mAs). The experimental group exhibited significantly higher image noise compared to the control group, and a lower signal-to-noise ratio and the total radiation dose. No statistical differences in aortic CT values, subjective image quality scores, operation duration and complication rates. Technique efficacy was achieved in more than 98.2% of patients in both two groups. Spectral shaping technology significantly reduces the radiation dose for patients undergoing CT-guided lung tumor MWA compared to the standard-dose protocol, without compromising image quality, operation duration or treatment efficacy. Trial registration number ChiCTR2000032481.