Abstract: Objective To study spiral CT three-dimensional reconstruction technique for non-small cell lung cancer radiotherapy target volume delineation of the accuracy.Methods Application of spiral CT scan and TOMOCON image system.In lung lesions of normal two-dimensional CT and respectively by two-dimensional CT combined with spiral CT three-dimensional reconstruction technique target volume.The target volume is calculated and compared longitudinal diameter and size.Results 48 cases of lung cancer patients CT Tumor image:gross tumor volume(18.85~380.63cm³),median volume 103.60cm³;Two-dimensional CT combined with spiral CT three-dimensional reconstruction results:target volume(24.05~420.57cm³)median volume 130.55cm³.Two sets of data by matching t test,analysis results P= 0.037.Two groups of results showed that the average diameter difference is 1.5±0.5mm.Longitudinal diameter difference is 3.0±1.5mm on average.Conclusions Spiral CT three-dimensional reconstruction technique is advantaged to delineate non-small lung cancer radiotherapy target volume.It is a complement of conventional CT scan in non-small cell lung cancer radiotherapy target volume delineation.