The invention discloses a technology for preparing an alkali-activated material by the use of cassava residue, comprising the following steps: (1) cassava residue pretreatment: putting cassava residueinto water, cooling with boiling water, taking out the cassava residue and air-drying and drying in a drying oven, and crushing the dried cassava residue in a pulverizer to obtain cassava residue powder; (2) preparation of an alkali-activated material test mold: putting the cassava residue powder, blast furnace slag, kaolin, a reinforcing agent and fly ash into a reactor, uniformly stirring, slowly adding water glass, carrying out ultrasonic vibration for 30-45 min, stirring for 5 min and then carrying out injection molding to obtain the test mold; and (3) maintenance: vibrating the test moldon a mortar vibration compaction table for 2 min so as to remove bubbles in the test block, sealing the test mold with a polyvinyl chloride preservative film, and maintaining at 60 DEG C until the predetermined period so as to obtain the alkali-activated material. The prepared alkali-activated material has high strength, and the production cost is reduced. The product quality is stable and controllable, and the product has high market promotion value.