The invention relates to a water-retention and sand-fixing liquid mulching film and a preparation method thereof, and belongs to the technical field of agricultural production. The liquid mulching film comprises components in parts by weight as follows: 30-50 parts of ultrafine silica sol or nano-silica, 40-100 parts of carboxymethyl cellulose, 20-30 parts of N-isopropylacrylamide, 1-5 parts of ferrocene, 0.02-0.3 parts of a cross-linking agent and 0.4-1.2 parts of an initiator, wherein the solid content of the ultrafine silica sol is 10wt%-30wt%, and the particle size of silica is 1-100 nm. The liquid mulching film forms colloid easily with water, soil particles can be connected, structureless and dispersed sand soil is connected to form an elastic stable object, and a net-shaped film with good film performance and high strength is formed; one the one hand, surface pores of soil can be sealed, and soil moisture volatilization is blocked; on the other hand, moisture permeation is not inhibited, good water retention, soil moisture preservation and sand fixing functions are realized, and the performance of a desert and dry soil is improved effectively.