Abstract: The waterborne anionic polyurethane emulsion (PU) synthesized by using 4, 4'-methy-lenebis phenylisocyanate (MDI) was mechanically blended with the polyacrylate latex emulsion (PA).The effects of the different proportion of PU and PA on the structures and properties on the composite materials have been studied.It has been revealed that polyacrylate (PA) and polyurethane (PU) had a certain compatibility, which resulted in improving the water resistance and thermal stability of the PU/PA composites obviously.