The invention discloses low-viscosity and long-term-retrogradation-resistant tartaric acid starch ester and a preparation method and application thereof. The preparation method includes: activating starch, to be more specific, regulating the water content of the starch to 25-40%, and activating in an extrusion-expansion machine, wherein the three-stage temperatures of the extrusion-expansion machine are respectively 30-40 DEG C, 40-50 DEG C and 50-60 DEGC; drying the activated starch; adding, by the dry basis weight of the starch, 0.5-6% of tartaric acid, adding water to achieve sufficient dissolving at 40-55 DEG C, mixing the tartaric acid in a mixer, mixing slurry, performing esterification reaction, performing liquid-removing washing, and performing drying treatment. The preparation method of the low-viscosity and retrogradation-resistant tartaric acid starch ester has the advantages that the method is simple in process, short in processing time and low in cost; the peak viscosity of the prepared starch ester is 300-480cP, the final viscosity of the starch ester is 90-525cP, the retrogradation value of the starch ester is 100-150cP, the solubility of the starch ester is 4.2-6.0%, and the starch ester is excellent in comprehensive performance.