Inbuilt emulsified waterborne polyurethane was synthesized via the reaction of polyester glycol with toluene diisocyanate and dimethylol propionic acid. The structure and properties of the products were characterized by FTIR, DSC and TGA etc. The results show that with the R(n(—NCO)/n(—OH) value increasing, the level of microphase separation increased, but the thermal resistance decreased. Three degradation stages were found in polyurethane dispersions, 190℃, 275℃, 360℃, respectively. The first and second rate of weight loss stages increased as the DMPA content increased, while the third rate of weight loss stage decreased. The comprehensive performance of WPU was the best when the value of R was 1.25 and DMPA content was at about 9 %.