Objective To evaluate clinical value of gemstone CT low dose scanning for early diagnosis of lung cancer. Methods The clinical data of 800 cases of physical examination in our hospital from March 2015 to March 2016 were analyzed retrospectively, 40 patients were diagnosed as early lung cancer by spectrum CT and were divided into experimental group, 24 patients were diagnosed as early lung cancer by spiral CT as control group. Compare and analyze the tube voltage, tube current, CT dose index, total radiation and early lung cancer imaging features of the two groups. Results Compared with the control group, the tube voltage, the tube current and the CT dose index in the test group were significantly lower than the control group (P<0.05). The thickness of the test group, the interval of the layer and the range of the matrix were compared with the comparison group, and the difference was not statistically significant (P>0.05). Two different dose CT scan can clearly suggest pulmonary nodules, showed lesions shadow size, shape, position and adjacent structures, etc., to identify lesions were material, cavitating nodules or high density small piece of shadow, clear present lesions border points leaves or burr), two groups of image contrast lungs, showed little differences of mediastinal structures, etc. Conclusion Gem spectrometry low dose CT scanning can ensure the quality of image, clear display characteristics of early lung cancer pathological changes, and reduce X-ray scan dose, which is safe and effective, simple and cheap, has significant clinical value in the early diagnosis of lung cancer, can be widely used in clinical.