Objective To explore the preliminary study of the four-dimensional CT-based respiratory gating applications in the IGRT treatment of lung cancer .Methods 38 patients′ were scanned with 4D-CT ,and could got 10 images:0-90% each one ,and then two kinds of radiation treatment plans :Plan-3D and Plan-4D were used ,respectively .Treatment of the patients in the IGRT mode with Plan-4D and following up were done in two months after treatment to evaluate the efficacy and complication probability . Meanwhile evaluation of the two plans by the volume histogram was done .Results The displacement of lung tumor respiratory mo-tion was different in three dimensions ,especially in the Vertical direction ,about(9 .1 ± 2 .2)mm .Accuracy of the distance was 2 .6 mm .The Plan-4D′s CTV was bigger than Plan-3D ,but its PTV was less than the Plan-3D significantly ,at the same time its lung V20 ,MLD were both less than the Plan-3D ,and the difference was statistically significant(P< 0 .05) .The total efficiency(CR+PR)was 77 .78% (28 case);the incidence of 1 ,2 ,3 acute radiation-induced lung injury were 86 .11% ,11 .11% ,2 .78% ,respectively ;the incidence of 1 ,2 acute radiation esophagitis injury were 80 .56% ,8 .33% .Conclusion The respiratory gating techniques based on 4D CT applied in image guided radiotherapy of lung cancer in clinical is feasible ,and it can reduce the volume of the planning tar-get volume ,and help to improve the accuracy of radiotherapy .The degree of respiratory motion is significantly different in individu-als ,and expanding outside the target ranges should be individualized .