The invention provides egg white-like liquid triple composite modified starch and a preparation method thereof, and belongs to the technical field of modified starch processing. The preparation methodof the modified starch comprises the following steps: (1) size mixing; 2, alkalization; 3, etherification; 4, esterification; 5, oxidation; (6) washing and dehydrating. According to the method, a one-step wet production process is formed by adopting etherification, esterification and oxidation procedures, the reaction is completed at one time, drying and dehydration links in step-by-step operation are reduced, the product quality is stable, energy is saved, emission is reduced, and the production cost is reduced; the product produced by the method has the characteristics of viscosity, transparency and stability similar to those of egg white liquid; the egg white liquid has good compatibility and permeability with essences, spices and other seasonings, has better processability than egg white liquid, is high in high-concentration acid, sugar, salt and mechanical resistance, can effectively improve the quality of egg products, and can be widely applied as a substitute of the egg white liquid products.