Abstract: The microstructure evolution and the hardness change rule of GH2036 alloy Φ150 mm bar solution treatment at 1120~1240 ℃ are studied by optical microscope and SEM and HB hardness testing device. Studies have shown that there are two types of rich Cr and Nb-V carbide in the forging microstructure of GH2036 alloy after forging air cooling, most of carbides are backdissolved and the grain size is basically uniform after 1220 ℃solution treatment. The HB hardness number of the alloy is reduced with the increase of heat treatment temperature, but the HB hardness number increases from 185 to 193 at temperature increasing from 1160 to1200 ℃, this is mainly due to the large amount of carbides solving back to matrix.