The invention provides modified hyperbranched poly(ester-amide), and a preparation method and application thereof, and belongs to the field of paint dispersants. The preparation method of the modified hyperbranched poly(ester-amide) comprises the steps that alcohol amine and aromatic acid/anhydride are added into a reactor; dimethylformamide is added for dissolution; a catalyst is added for uniform mixing; heating to 80 to 150 DEG C; reaction is performed for 0.5h to 4h at ordinary pressure; then, a reaction system is vacuumized; the reaction is continuously performed for 1 to 5h under the pressure reduction condition; the zero generation of terminal carboxyl group hyperbranched poly(ester-amide) is obtained; iteration reaction is performed; the Nth generation of hyperbranched poly(ester-amide) is obtained; the Nth generation of hyperbranched poly(ester-amide) is ground into powder; then, the powder is slowly added into a sodium hydroxide water solution or ammonium hydroxide; reaction is performed to obtain the Nth of modified hyperbranched poly(ester-amide). The modified hyperbranched poly(ester-amide) provided by the invention has a high dispersion effect on paint; the compatibility is high; the adhesive force of the paint on a substrate can be obviously improved; the coating effect of the paint is improved.