Abstract: In order to analyze the effect of the local circumferential breakdown of the cement sheath on the casing mechanics properties in thermal recovery wells, the finite element model of cement sheath circumferential discontinuity is established using the ABAQUS program. The variation laws of casing stress and deviation is studied during the process of steam stimulation. The result shows that the borehole temperature fluctuates due to the cement sheath circumferential discontinuity. As a result, the temperature outside the casing-wall and the borehole temperature without cement sheath are lower than that with perfect cement sheath. Cement sheath discontinuity exerts great effect on the equivalent stress peak value. The equivalent stress peak value Von Mises declines as the degree of cement sheath circumferential discontinuity increases. When the cement sheath circumferential discontinuity is 30°, the casing deforms much in the radial direction. It will drop as the degree of cement sheath circumferential discontinuity increases. The analysis provides theoretical basis for the mechanism research of casing failure in thermal recovery wells. 　　　