Firstly, the prepolymer of polyurethane (PU-HEMA) was synthesized using poly(propylene oxide glycol) (PPG), isophorone diisocyanate (IPDI) and dimethylol propionic acid (DMPA) as main monomers, and using hydroxyethyl methacrylate (HEMA) as grafting reagents. Then, using miniemulsion polymerization technology, the waterborne polyurethane - polyacrylate composite emulsion (PU-PA) was successfully prepared with copolymerization of acrylic ester and PU-HEMA. The effects of monomers dosage, ratio of PA/PU on the properties of PU-PA emulsion were investigated. It was found that the optimal dosage of DMPA, HEMA was 3 % and 6% respectively. The PU-PA was characterized by FT-IR, TG and SEM. The PU-PA was also applied to prepare waterborne polyurethane-acrylate composite coating (PU-PA-C) with the addition of pigments and fillers, such as diatomite, bentonite, etc. PU-PA-C meets the standard for interior wall coatings and architectural coatings. Its water absorption rate get to 206 %, and wash resistance is more than 900 times. The coatings showed strong performance of water absorption / desorption, which could be used as the interior wall coating in the building.