An　isothermal　compression　experiment　of　X2A66　alloy　was　carried　out　by　a　Gleeble-3500　thermal　simulator　within　the　deformation　temperature　range　of　623.15　similar　to　743.15　K　and　the　strain　rate　range　of　0.001　similar　to　10　s(-1).　The　alloy　peak　stress　constitutive　equation　and　processing　map　were　established　by　a　hyperbolic　sine　function　and　a　dynamic　materials　model.　The　results　show　that　flow　stress　of　the　alloy　decreases　with　the　increase　of　deformation　temperature　while　increases　with　the　increase　of　strain　rate.　In　addition,　the　strain　rate　has　no　effect　on　temperature　sensitivity　of　X2A66　alloy;　the　rate　sensitivity　at　high　strain　rate　above　0.1　s(-1)　is　higher　than　that　at　low　strain　rate.　In　isothermal　compression　experiment　of　X2A66　alloy,　the　relationship　between　the　peak　flow　stress　and　strain　rate　satisfies　the　hyperbolic　sine　function　and　the　constitutive　equation　is　(epsilon)over　dot　=5.09　X　10(9)[sinh(0.019　sigma)](4.54414)exp(-145.377/RT).　In　the　range　of　test　parameters,　the　instability　zones　of　X2A66　alloy　are　mainly　concentrated　in　the　area　of　high　strain　rate.　The　peak　area　of　dissipation　efficiency　is　in　the　strain　rate　range　of　0.01　similar　to　0.3　s(-1)　and　the　deformation　temperature　range　of　700　similar　to　743　K,　which　is　the　best　thermal　processing　zone　for　X2A66.