Objective To analyze feasibilityof application of 64-slice spiral CT low dose contrast medium in CT pulmonary angiography. Methods 64 patients suspected clinically as pulmonary embolism in our hospital from November 2012 to November 2014 were divided by random lot method into two groups, 32 cases in each group, low dose group used 30mL contrast medium, routine dose group used 70mL contrast medium. Vasa publica enhanced CT value, pattern noise, signal-to-noise ratio, contrast-tonoise ratio, subjective image quality score and incidence of adverse reactions in the two groups were compared, sensitivity, rate of missed diagnosis, specificity and misdiagnosis rate in the diagnosis of pulmonary embolism in the two groups were compared. Results Pulmonary vein vessel enhanced CT value in routine dose group was significantly higher than low dose group(P<0.05), incidence of adverse reactions in low dose group was 12.5%, which was significantly lower than routine dose group (43.75%) (P<0.05). Conclusion Application of 64-slice spiral CT low dose contrast medium in CT pulmonary angiography can meet the demand of clinical diagnosis, there is no significant difference in image quality, accuracy, sensitivity, specificity in the diagnosis of pulmonary embolism compared with routine dose, decreases incidence of adverse reactions of patients, is worth using in clinical practice.