Abstract: XMAC logging tool is able to continuously measure in underground. For every reservoir sedimentary unit, it can not only measure the maximum horizontal principal stress, minimum horizontal principal stress, the maximum horizontal principal stress orientation, but the lithology mechanical parameters can be obtained, such as density, fracture pressure, poisson's ratio, young's modulus, and shear modulus. It will help us to study rock mechanical characteristics of the reservoir. So the technical supports will be provided for us to determine the correlation between geological stress and casing damage, and to establish the correlation between rock mechanical parameters and casing damage. Compared with non-casing-damage area, the principal stress and fracture pressure was very high, poisson's ratio was large, and the shear modulus was small in the larger index bed casing-damage area. So the mechanical characteristics can be used to establish the formation or existence of casing damage area in the standard layer. Compared with the normal well area, the principal stress and fracture pressure were higher, poisson's ratio was larger, the shear modulus was small, and the principal stress orientation was deflected. So the mechanical characteristics can be used to establish the formation or existence of casing damage area in reservoir section. Higher fracture pressure, bigger poisson's ratio, smaller shear modulus, and greater differences in stress are internal cause of casing damage in N2 index bed. Plane stress differences between regions are standard parts of the external impetus of casing damage. The rock mechanical characteristics which bigger poisson's ratio, smaller shear modulus, fracture pressure is higher, and so on, are the internal causes of casing damage in reservoir section. The changes of geological-stress field and formation-pressure-field are the external causes of casing damage in reservoir section. The casing damage in reservoir section is the result of the effect of internal and external causes.