Objective To evaluate the value of post-processing techniquos of multi-slice spiral CT(MSCT) in diagnosis of small peripheral lung cancer. Methods 36 patients with small peripheral lung cancer(≤20mm in di-ameter) who had been proved by pathology were eoueeted. After MSCT scanning ,3D reconstruction images were made by MPR,SSD and VR,then compared with axial thin-slice images. Results The sensitivity of MPR on vascularnotch sign,lobulation and spiculated sign was higher than that of axial thin-slice images. The sensitivity of SSD on peural sign was higher than that of axial thin-slice images. The sensitivity of VR on vascularnotch sign and lobulation was higher than that of axial thin-slice images. Conclusion The post-processing techniques of MSCT have high value on diagnosis of small peripheral lung cancer. More information could be collected when many kinds of post-processing techniques were used.