The invention provides a 
cement slurry with long-term-integrity 
cement sheath for a heavy-oil thermal-
recovery well. The 
cement slurry comprises, by weight, 100 parts of thermally responsive cement, 25 to 65 parts of water and 0.2 to 8 parts of a 
cement slurry aid. The thermally responsive cement comprises 30 to 60 parts of 
oil well cement, 10 to 20 parts of active 
silicon powder, 0 to 10 parts of hollow glass beads and 10 to 50 parts of a thermally responsive 
composite material. The thermally responsive 
composite material comprises 20 to 30 parts of clay mineral, 10 to 20 parts of 
fly ash and / or vulcanic ash, 5 to 20 parts of rubber 
powder and / or latex 
powder, 3 to 10 parts of carbon 
fiber, 10 to 15 parts of nanometer 
silicon dioxide, 5 to 10 parts of calcined magnesia, 10 to 20 parts of ultrafine superfine 
slag powder and 5 to 10 parts of inorganic 
whiskers. The 
cement slurry provided by the invention can solidify at normal temperature; and set cement can 
resist long-term high temperature, and the mechanical properties and thermal properties of the set cement in a high temperature environment are integrally adaptive to strata and casing pipes.