Abstract: The φ7.32 μm×3 mm short carbon fibers with 0.10%-0.50% (mass fraction of refractory powders in slurry)was added into the silica sol coating in investment casting to enhance the strength of the shell. The rheological properties of the coatings for shell making with different fiber content were studied. The results show that when the fiber content is 0.30wt%, the apparent viscosity of the coating is the highest, reaching 150.35×10 ^-3 Pa·s, and the apparent viscosity is increased by 22.58%compared with that of the coating without fiber. At the same time, the thixotropic ring area reaches the maximum value of 240.01 Pa·s^-1, which increases by about 265.59%.The effect of fiber addition on the suspension of coating is not significant. When the amount of fiber is 0.30wt%, the suspension rate reaches the highest value (94.23%), which increases only 3.41%compared with that of the coating without fiber.