The invention relates to a bifunctional acrylate monomer obtained via photopolymerization and a preparation method thereof. Structural formula of the bifunctional acrylate monomer is represented by a formula in the invention. According to the preparation method, polyethylene glycol octylphenol ether, epoxy chloropropane, and acrylic acid are taken as raw materials; at alkaline conditions, polyethylene glycol octylphenol ether and epoxy chloropropane are reacted so as to obtain an intermediate product; the intermediate product is subjected to appropriate processing, and then is subjected to ring opening esterification with acrylic acid so as to obtain an object product; size shrinkage of the bifunctional acrylate monomer in polymerization is low; the two ends of the bifunctional acrylate monomer are connected with hydroxy groups, so that the bifunctional acrylate monomer possesses certain hydrophilic performance; product volatility is lowered; adhesive force is relatively high; and the bifunctional acrylate monomer can be widely used for fields such as painting and adhesive. Raw material cost of the preparation method is low; reaction steps are few; preparation period is short; operation is simple; controlling is convenient; by products are few; complex waste water processing is not necessary; and the preparation method is more suitable for industrial production.