By studying the image characteristics of primary lung cancer on spiral computed tomography compared with cytologyclassification in 93 patients, we draw some conclusions as follows: - Small cell carcinoma: Occupying 9.7 percent more common in males (77.8 percent). X-ray images show tumors usually in the center (77.8 percent) or large mediastinal images. The outer of tumors often not smooth, with spines (77.8 percent), no cavitaion. - Squamous cell Carcinoma: Making up 58 percent rate, occur more frequently in men (80.4 percent). Usually the outer fringes (77.7 percent), the tumors are often heterogeneous, having cave necrosis (2 percent). - Adenocarcinoma: Occupying 28 percent, common in women (76.9 percent). The tumor usually localized in the periphery (84.6 percent) than in the center (15.4 percent), smooth edge (19.6 percent), tumor margins often have spines (65.3 percent), citrus (15.3 percent). The tumor can destroy cave cancer (18.1 percent). - Large cell carcinoma: being 4.3 percent rate, the tumor usually localized in the peripheral lung (75 percent). Common CT image is the diversified shapes with spines (75 percent).