Microstructure　evolution　and　phase　transformation　of　Co-12Al-10W　superalloy　during　heat　treatment　were　investigated　by　means　of　electric　microscopy.　The　results　show　that　primary　CoAl　phase　appeares　in　as-cast　alloy,　and　it　is　solid　solved　completely　after　solid　solution　at　1300℃　for　8　h　with　precipitation　of　μ　phase.　The　γ/γ＇　matrix　appeares　after　aging　at　900℃　for　50　h　and　the　main　secondary　phase　is　μ　phase　in　the　early　stage　aged　alloys.　Small　amount　of　coexisting　cases　including　DO19,　B2　and　μ　phases　begin　to　appeare　in　prolonged　aging　alloys　while　it　increases　quickly　in　alloys　after　aging　treatment　for　600　h.　A　large　quantity　of　acicular　B2　phase　precipitates　in　alloys　aged　for　600　h　in　the　same　time.　Diffraction　patterns　indicate　a　special　orientation　relation　between　base　and　precipitates　as　follows:　[111]B2//[110]γ＇,　(011)B2//(111)γ＇,[001]μ//[110]B2//[001]DO19,　(112)B2//(100)μ//(100)DO19,(110)B2//(027)μ//(010)DO19.　The　special　relationship　can　be　attribute　to　a　related　structure　among　them.　The　phase　transformation　can　be　attribute　to　the　diffusion　of　element　of　tungsten　during　aging　treatment.　©　2016,　Editorial　Office　of　＂Jinshu　Rechuli＂.　All　right　reserved.