Objective To assess the value of pulmonary CT angiography(CTA) in diagnosis and clinical observation of pulmonary embolism(PE) by Multi-slice CT (MSCT). Methods One hundred and sixty three patients from 2013.01 to 2014.12 who were diagnosed or suspected with PE underwent CTA and the images were transferred to the computer workstation subsequently post-processed using volume rendering (VR),multiplaner reformation (MPR),curved planar reformatting (CPR), maximum intensity projection (MIP) to analyse the manifestation of PE and the variation on clinical observation of PE. Results One hundred and twelve cases were positive,and else were negative.Pulmonary vessels with embolism were conformed by the direct signs of CT which was filling-defect of saddle type, central type, eccentric type or complete type. Eighty-three patients with pulmonary artery completely blocked were improved in varying degrees after clinical treatment with thrombolysis by re-examination of CTA, and forty-nine of that were completely cured. Conclusion It is conformed that CTA in diagnosis and clinical observation of pulmonary embolism has an important application value.