In order to study the spectrum characteristics of Yb2＋ ions in the silica glass,the flame fusion process is put forward to prepare the Yb2＋/Yb3＋ co-doped silica glass.F irst of all,the forming process of Yb2＋ ions in the adopted process is analyzed.The absorption characteristics and emission charact eristics of the prepared Yb2＋/Yb3＋ co-doped silica glass are analyzed.The analysis results show that the prepared Yb2＋/Yb3＋ co-doped silica glass has absorption peaks in the ultraviolet (UV) and visible wavelengths of 260nm,320n m,359nm,400nm and 437nm as well as the near infrared wavelengths of 910nm and 975nm,and has the emission peak in the visi ble wavelength of 530nm.The upconversion luminescence around 500nm is observed when the prepared Yb2＋ /Yb3＋ co-doped silica glass is irradiated by the femtosecond laser.What’s more,the production mechanism of t he upconversion luminescence of the Yb2＋/Yb3＋ co-doped silica glass is analyzed.It is proved th at the forming reason of the upconversion luminescence is that two-photon is absorbed simultaneously by Yb2＋ ions in the Yb2＋/Yb3＋ co-doped silica glass.