Abstract: This is a paper in the field of mineral ceramic materials. In order to enhance the mechanical properties of cemental sand materials and improve the utilization rate of mineral resources, the reinforced samples were made by mixing blast furnace slag fiber with river sand, cement and water. The effects of the content and length of furnace slag fibers on the strength characteristics of reinforced specimens were studied by unconfined compression tests. The results show that the unconfined strength of cemental sand samples increases with the increase of the content of furnace slag fiber, but the increase rate decreases obviously when the content of fiber reaches 0.3%. Using 5 mm and 10 mm fiber length to modify the cemented sand, the strengthening effect of the long fiber on the strength of the cemented sand is 1.25~1.55 times that of the short fiber under the condition of the same dosage. Through the microscopic morphology observation, it is found that the addition of furnace slag fibers to the cemental sand can improve the degree of adhesion between particles and agglomeration effect, and then enhance the strength and toughness of the cemented sand.