The invention discloses a wood adhesive and a preparation method thereof. The wood adhesive comprises the following raw materials in parts by weight: 20-90 parts of dicyanoacrylate, 10-30 parts of alkoxy cyanoacrylate, 10-20 parts of mango dietary fibers, 10-12 parts of trimethylsilyloxy phenyl polydimethylsiloxane, 20-30 parts of sodium polyacrylate, 10-60 parts of astaxanthin, 20-40 parts of rubber and 10-15 parts of an auxiliary. The preparation method comprises the following steps: adding the dicyanoacrylate, the alkoxy cyanoacrylate, the trimethylsilyloxy phenyl polydimethylsiloxane, the sodium polyacrylate, the astaxanthin, the rubber and the auxiliary are uniformly mixed, heated to 70-80 DEG C, stirred and allowed to react for 2-3 hours and cooled to room temperature, and the mango dietary fibers are added, the raw materials are heated to 100-120 DEG C, allowed to react for 20-30 minutes and then cooled. The wood adhesive has good adhering performance, and the addition of the mango dietary fibers improves the adhering capability of the wood adhesive.