Objective To quantitative analyze the change of the position accurately using Elekta synergy accelerator by KV-CBCT (kilovoltage cone-beam computed tomography) for patients of non-small cell lung cancer(NSCLC) with stereotactic body radiation therapy(SBRT), design plan of NSCLC with SBRT from CTV to PTV to offer reference to external data, to provide for a reasonable margin of PTV the basis for clinical doctors. Methods To collect from March 2013 to February 2014, using Elekta synergy accelerator radiotherapy for 10 cases of patients with NSCLC, using KV-CBCT scans before radiotherapy, acquired the XVI were registered to planning CT and the set up errors were obtained on the X axis (left-right, LR), the Y axis (superior-inferior, SI) and Z axis (anterior-posterior, AP) and the errors correction, then compared statistically. Results The set up errors on the X axis (left-right, LR), the Y axis (superior-inferior, SI) and Z axis (anterior-posterior, AP) were (0.34±0.21)cm, (0.47±0.17)cm and (0.37±0.19)cm, in three dimensional directions, respectively; the set up errors correction on X, Y, Z were(0.09±0.14)cm, (0.11±0.15)cm and (0.06±0.12)cm, respectively. According to vanHerk formula Mptv=2.5Σ+0.7σ, calculated Mptv of X, Y, Z were 0.41cm, 0.58cm, 0.43 cm directions, respectively. Conclusion By the KV-CBCT for set up errors correction of NSCLC with SBRT, can greatly reduce all kinds of system error and random error, to provide the margin data when design the radiotherapy plan. According to the results of residual set up errors evaluation, 0.6cm should be applied to the margin of PTV.