Abstract: To solve the problems of high brittleness, low tensile strength, poor impact resistance and fracture resistance of the cement stone in oil wells, a multi-scale fiber toughener BCE-230S was formed by selecting inorganic fibers in three different scales and conducting orthogonal tests for compound. In addition, the effects of the dosage of BCE-230S on the construction performance of cement slurry and the mechanical properties of cement were investigated, the optimal dosage was determined, by which a tough cement slurry system with multi-scale fiber was formed. The results showed that the splitting tensile strength, compressive strength and impact resistance of the cement stone were significantly improved when compared with common cement.Young’s modulus decreased significantly and the construction performance was ideal. The tough cement slurry system with multi-scale fiber was applied in the low permeability reservoir in the Jidong Oilfield for more than 10 times in the well, and the cementing quality of the two cementing surfaces was measurably improved compared with that of adjacent wells. Fracturing in later stage was successful, and no fluid channeling was observed during well testing. The results indicated that the tough cement slurry system with multi-scale fiber can effectively solve the problem of brittleness of cement stone in oil well, so as to ensure the integrity of the wellbore and the long-term cementing quality, with a potential for wide application.