The invention belongs to the technical field of food processing and discloses stable food-grade low-fat lard-based oil-in-water emulsion and the preparation thereof. The stable food-grade low-fat lard-based oil-in-water emulsion is prepared from lard, lard-based monoglyceride, lard-based diacylglycerol, sodium caseinate and distilled water, wherein the mass ratio of the lard to the lard-based monoglyceride to the lard-based diacylglycerol to the sodium caseinate to the distilled water is 5:(0.5-2):(3-4.5):1:89. The lard-based emulsion fat ball particles are small, the emulsion liquid drops are distributed uniformly, the average particle size of the fat balls maintains about 0.2 to 7.0 microns when the fat balls are placed within 24 hours, and the system has high stability; in the prepared lard-based emulsion, the lard content is 5 percent, the total fat content is 10 percent and the fat content is low; when the lard-based emulsion is applied in the field of food, the lard-based emulsion contributes to avoidance that eaters take excessive fat, and is good for health.