Direct　measurements　of　the　magneto-caloric　effect　of　Gd5Si2Ge2　alloys　under　heat　treatment　conditions　are　investigated　by　measuring　adiabatic　temperature　change　(Delta　T　(ad))　in　a　magnetic　field　of　1.5　T　using　a　homemade　magnetocaloric　effect　measuring　apparatus.　The　crystal　structure,　microstructure　as　well　as　the　chemical　composition　of　the　alloys　are　measured　using　X-ray　diffraction　(XRD),　scanning　electron　microscope　(SEM)　with　energy　dispersive　X-ray　Detector　(EDX).　It　is　found　that　the　microstructure　of　the　alloys　could　be　fully　homogenized　and　the　impurities　in　the　alloys　could　be　remarkably　removed　via　appropriate　heat　treatment.　As　a　result,　the　maximum　adiabatic　temperature　change　(Delta　T　(ad))　of　the　alloy　annealed　at　1573　K　increases　by　105%　from　1.9　to　3.9　K　for　a　magnetic　field　change　from　0　to　15　kOe　when　compared　to　the　as　arc-melted　material,　while　the　magnetic　ordering　temperature　slightly　reduced.