In this paper, the energy transfer processes between Pr 3+ ions and Yb 3+ ions were studied in upconversion luminescence of Pr, Yb:ZBLAN. There are three ways for the energy transfer from Yb 3+ to Pr 3+ . Yb 3+ ions act as sensitisers in the upconversion luminescence of Pr 3+ ions. There are also three energy transfer paths from Pr 3+ ions to Yb 3+ ions, which quenches the luminescence of Pr 3+ ions and results in saturation of luminescence of Pr 3+ ions with the increasing concentration of Yb3+ ions.