The invention discloses a polymer concrete defoaming agent and a preparation method and application thereof. The polymer concrete defoaming agent is a surfactant monomer homopolymer containing one hydrophobic chain segment and one hydrophilic chain segment, wherein the hydrophilic chain segment is polyethylene glycol containing 4-10 repetitive units, and the hydrophobic chain segment is linear chain alkyl containing 11-17 carbon atoms; an alkyl epoxy compound A reacts with enol B to generate a monomer C with a hydrophobic chain segment R, then through ring opening polymerization of ethylene oxide, the monomer C carries a hydrophilic chain segment to form a monomer D, and finally through copolymerization of free radicals of the monomer D, the defoaming agent is prepared. Compared with a traditional single chain defoaming agent, the polymer concrete defoaming agent is higher in surface activity and defoaming efficiency, the compatibility between the polymer concrete defoaming agent and an additive is good, generation of big bubbles in newly mixed concrete can be inhibited in a short time, the content of air in the concrete is reduced, and therefore the hardening strength and durability of the concrete are improved.