This paper is aimed at the problems of weak cement sheath, weak impact strength, low compressive strength, and low bonding quality in slim-hole cementing. The cement slurry system was improved by edding self-developing elastic emulsion combined with toughening fiber. The authors compared the influence of different toughening materials on the mechanical properties of cement stone. The evaluation results show that the cement slurry system exhibits good rheological properties through the combination of fiber and elastic emulsion. Pumping resistance is small, high temperature and high pressure filter loss is less than 30 mL, slurry is stable, no free water is regestered, the cement stone also shows good shrinkage resistance, and thickening time can be adjusted to 3-5 h. In addition, in terms of mechanical properties, the impact strength of cement stone containing 0.3% carbon fiber + 15% elastic emulsion is greater than 2.2 KJ-m(2), the compressive strength at 24 h is greater than 20 MPa, the resistance to gas is 15.6 MPa, and the shear strength is greater than 3.5 MPa. The tensile strength is greater than 300 KPa, which fully meets the requirements of field applications.