Alumina fibers, with an aspect ratio ranging from 9 to 27, were utilized as the reinforcing materials for silica-sol ceramic shell molds, and the impact of different alumina fiber additions on the green bending strength, room- and high-temperature bending strength, and self-weight deformation of ceramic shell molds was investigated. The green bending strength of shell molds is the maximum at an alumina fiber addition amount of 0.2wt.%, reaching 6.20 MPa. Further increases in alumina fiber content do not significantly affect the green bending strength. As the alumina fiber addition amount increases from 0.2wt.% to 1.0wt.%, the bending strength and the resistance to self-weight deformation of the ceramic shell molds at high-temperatures show a pattern of first increase and then decrease. The shell molds after sintering exhibit the highest room-temperature strength of 17.33 MPa and the highest high-temperature strength (18.97 MPa at 1,100 °C; 17.78 MPa at 1,200 °C; and 15.3 MPa at 1,300 °C), and the smallest self-weight deformation of 0.022% at 1,000 °C when the alumina fiber addition is 0.6wt.%. The appropriate amount of fibers in the shell mold matrix consume the energy required for crack growth

through mechanisms such as bridging and pulling-out, thereby improving the strength of shell molds. In summary, the comprehensive performance of the shell molds is the best when the fiber addition amount is 0.6wt.%.