Purpose:To analyse the X-ray stereotactic treatment process during which errors induced and to establish a QA program and its checking frequency.Materials and Methods: Checking the parallelism and the asymmetry of the opposing plates containing localizing wires of the CT(MRI) stereotactic localizing frame; Checking the precision of the mechanical scaler of the target positioner; The influence of the laser alignment system in the treatment room of linear accelerator ; Determining the overall precisions available by a X-ray stereotactic treatment system; and small beam's data acquisition means, etc.Results: An overall target positions'precisions of 2.4mm,2.6mm(1mm CT slice thickness), and 3.7mm, 3.8mm (3mm CT slice thickness) for single and fractionated X-ray stereotactic irradiation respectively can be achieved if a QA program be seriously carried out.Conclusion: It is an essential to establish a comprehensive QA program to guarantee a good treatment precision of X-ray stereotactic irradiation.