YAG-Ce, Nd, and Yb phosphors with a triple-doped system are prepared by conventional solid-state reaction method. The fluorescence emission and excitation spectra are measured and analyzed. The influences of Yb3+ doping concentration on the emission of Yb3+ and Nd3+ in YAG-Ce, Nd, and Yb are studied. The fluorescence decay spectra, lifetime, and energy transfer efficiency of Ce3+ in different host materials of YAG-Ce and Yb, and YAG-Ce, Nd, and Yb are also compared. Furthermore, the trends of fluorescence decay spectra and the lifetimes of Nd3+ and Yb3+ in YAG-Ce, Nd, and Yb with the increase of Yb3+concentration are discussed. Results indicate that YAG-Ce, Nd, and Yb are good candidates for downconverting phosphor, with energy transfer efficiency reaching as high as 82.8%.