The Gd 5 Si 2 Ge 2 and Gd 5 Si 2 Ge 1.9 T 0.1 (T: Mn, Fe, Co, Ni) series alloys have been prepared by arc-melting method and annealed at 1300°C for an hour. The phase formation and thermal hysteresis of the experimental alloys have been examined with the help of powder X-ray diffraction and optical metallographic combined with magnetic measurement. From XRD results, the alloy with the addition of Fe or Co is inclined to form the mixed Gd 5 Si 4 -type and Gd 5 Si 2 Ge 2 -type phase. Transition elements Mn and Ni result in the orthorhombic Gd 5 Si 4 -type phase formation in Gd 5 Si 2 Ge 1.9 T 0.1 (T: Mn, Ni) alloys. Magnetic measurement shows that all the four experimental transition elements could reduce the thermal hysteresis of Gd 5 Si 2 Ge 2 .