_{:The changes of microstructure and mechanical properties of GH3230 alloy plate after long-term heat exposure treatment at different temperatures (700-1000 ℃) and different times (1000-2000 h) were studied. The results show that the degree of dendrite segregation of as cast microstructure in the melting zone is significantly reduced after heat exposure treatment, andwith the increase of heat exposure temperature, the reduction effect is more obvious, and the grain structure is gradually formed. The tensile strength and yield strength at room temperature decreased and the elongation increased, which wasmainlycaused by the solubilizing of small granular (CrW)23C6 carbides in the heat affected zone and the coarsening of W6C carbides. With the increase of heat exposure temperature, the protractedrupturetimesignificantly decreases, whilethe endurance plasticity increases. The change of grain size and carbide coarsening are the reasons for fracture of welded plates at the base metal. No harmful phase such as TCP brittleness was found in the welded joint of GH3230 alloy welded plate. The alloy is suitable for long-term use as combustion chamber and blade.}