Hyperbranched polyesters (HBPE) were synthesized based on 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP) as a core molecule and 2, 2-bis (hydroxymethyl) propionic acid (bis-MPA) as an AB2 monomer. P-tert-butyl-benzoic acid (PTBA) was used as the modifier and obtained modified products with substituted degree vary from 10% to 75% (HBP-10M---HBP-75M, collectively called HBP-Ms). The structures and number–average molecular weights of HBPE and HBP-Ms were tested by Fourier transform-infrared spectroscopy (FTIR), 1H NMR spectra and Gel permeation chromatography (GPC), respectively. The result showed that the average branching degree (DB) of HBPE was about 0.47. The polymers were soluble in acetone, DMF, ethylacetate, diethyl ether, benzene, and dimethylbenzene, and insoluble in n-hexane. The HBP-Ms cured films displayed excellent properties including high hardness, gloss and excellent flexibility. HBP-10M and HBP-25M exhibit better solubility and film properties. Thermogravimetric analysis (TGA) disclosed that the PTBA could improve the thermal stability of HBP-Ms.