The invention relates to a preparation method for a loss-resistant wood fire retardant and belongs to the technical field of wood fire retardants. According to the method, kaolin is collected, ball-milled for powder preparation and composited with a sodium chloride solution, modified kaolin is prepared through roasting, and activated mixed kaolin powder is formed through composite roasting; then the activated kaolin powder is reacted with sodium hydroxide, and activated kaolin powder with microcellular structures is formed through sodium hydroxide alkalization treatment; and collagen and the activated kaolin powder are subjected to composite milling, collagen particles are adsorbed through the microcellular structures, and the wood fire retardant is prepared through composite ball-milling of the collagen, the activated kaolin powder, ammonium polyphosphate, melamine and other materials. The kaolin is adsorbed through activated microcells, and lignin on the surface of wood is bonded through the collagen, so that the loss resistance of the wood fire retardant is effectively improved, the service life of the wood fire retardant is prolonged, the durability of the wood fire retardant is improved, and the wood fire retardant is has wide application prospects.