Gd3Ga5-xAlxO12 single crystal has been grown by the Czochralski rechnique. It was ascertained as garent single phase material by X-ray photography. Experimental studies of the magnetization and susceptibility of Gd3Ga5-xAlxO12 have been carried out along the [111] crystal axis in the temperature range of 1.5 to 77 K, and compared with Gd3Ga5O12 (GGG).The primary results show that the susceptibility of this material obeys the Curie-Weiss law when the magnetic field is below 500(Oe), the ordering temperature is far below 1.5 K. The magnetization of GGAG is about 4% higher than that of GGG for magnetic fields greater than l0000(Oe). When the magnetic field is about 30000 (Oe). The Critical magnetic field of GGAG is about 4000(Oe) higher than that of GGG. It is shown that the substitution technique is efficient in searching after new working substance for magnetic refrigerator.