Abstract: In order to investigate the influence mechanism of fly ash microspheres on the workability and mechanical properties of fiber-reinforced cement-based composites (ECC), this paper prepared ECC samples by designing fly ash microspheres with different dosages (0%, 5%, 15%, 25%, and 35%), and conducted experimental studies on their flowability, compressive strength, and flexural strength.The test results show that the addition of fly ash microspheres to replace part of the silica fume can significantly improve the working performance of ECC. When the proportion of fly ash microspheres added is 15%, its fluidity reaches the maximum value, with an increase of 17.2%, which greatly improves the pouring quality of cement-based composite materials and the on-site construction efficiency. When the content of fly ash microbeads is between 0% and 25%, the compressive strength and flexural strength of ECC both reach 52 MPa and 13 MPa or above. When its dosage is greater than 25%, the degree of reduction in ECC compressive strength and flexural strength significantly increases. Therefore, fly ash microbeads as a composite component of cementitious materials can significantly improve workability while providing higher strength performance by optimizing the internal pore structure of the composite material. This study provides theoretical basis and practical guidance for the preparation of ECC composite materials with excellent mechanical and working properties.