A series of Re3+ (Re=Lu, Gd, La) co-doped YAG phosphors were successfully synthesized by a sol-gel combustion method and characterized with XRD and photoluminescent spectrum. The phase composition and luminescent properties of YAG:Ce under different Re co-doped concentrations were investigated. Doping only 50 mol% of La3+ to replace Y3+ sites, the main phase of sample has transformed into LaAlO3. While the concentration of Gd3+ reached 90~99 mol%, it was still cubic YAG. Lu3+ could replace Y3+ ions completely with the garnet structure. The location of the emission peak of Gd-codoped YAG:Ce3+ shifted to red region 21 nm corresponding to the maximum emission intensity before the appearance of GdAlO3. In addition, it had a 24 nm blue shift when Y3+ replaced by Lu3+ completely.