Mixed hammered ash is a kind of repair material with both hydraulicity and air hardening properties used in the restoration of Leshan Giant Buddha. To solve the problems of cracking and peeling caused by the influence of the environment on the repair materials of the head and face of the Buddha, hemp fiber (HF) and Calcium carbonate whisker fiber (CWF) are used to enhance this material. The results show that HF performs better than CWF in improving the flexural strength of materials, and the addition of CWF effectively enhances the toughness and splitting tensile strength of the material. The combination of the two can achieve a comprehensive strengthening effect. After 28 days of curing, the maximum increase in flexural strength of the composite specimens compared to the undoped specimens was 35.73%, and the maximum increase in splitting tensile strength was 20.88%, both of which were higher than those of the corresponding single doping group specimens. In addition, the performance of the composite group specimens in water resistance and acid resistance tests is better than that of the control group and the single addition group, indicating that the multi-scale fiber composite method helps to achieve a comprehensive improvement in material strength and weather resistance.