The waterborne soybean oil-rosin-based hyperbranched polyester was prepared from rosin, soybean oil, maleic anhydride and glycerol and characterized by FTIR, GPC and TG. The results showed that the preferred conditions for the preparation of the polyester are as follows: the dosage of soybean oil was 50% by mass of rosin, that of maleic anhydride was 20% by mass of rosin, and the hydroxyl-carboxyl ratio of raw materials was 0.86 by adding glycerol, esterification reaction temperature was 250℃, and reaction time was 3 h. Under these conditions, the number average molecular weight (Mn) of the prepared hyperbranched polyester was 1776, the weight average molecular weight (Mw) was 5305, the acid value was 49.9 mg/g and softening point was 67℃. The yellow transparent colloid solution was obtained after 3 hours of emulsification. TG results indicated that the decomposition of polyester was mainly concentrated in the ranging from 350℃ to 450℃, indicating that it had higher thermal stability. The particle size distribution of the hyperbranched polyester colloidal solution demonstrated that the average particle size of the whole system was 22.14 nm, which revealed that the polyester had good emulsifying and dispersing properties in water.