The investigation of the near-edge X-ray absorption fine structure(NEXAFS) of Na-induced Si(111)3×1 surface structure using the secondary electron partial yield method with synchrotron radiation is reported. Comparing the possible absorption models by the multiple-scattering cluster method, we find that the calculated results by using the Mnch model agree with the experiments.The sodium atom is absorbed on the top site with Na—Si bond length 0.3 nm.