The polyacrylate emulsion (PA) were synthesized by seeded semi-continuous emulsion polymerizations，which used as a coalescent of the hard resin latexes to replace small organic molecules, to prepare ultra-low volatile organic compound (VOC) contents waterborne wood coatings. Effects of Tg of PA, proportions and dosages of emulsifiers, and amounts of MAA on emulsion polymerization stability, properties and assistant-film-forming performance of PA were studied. It was found that the assistant-film-forming ability of PA was obvious increased with decreasing of polymer Tg from 0℃ to -20℃; and the gel contents of PA reduced from 0.83% to 0.10% with increasing of the reactive emulsifier contents; the PA average particle sizes could be reduced to 69nm with increasing of emulsifier dosage up to 2.1% and the assistant-film-forming ability of PA was enhanced as well; The total VOC content waterborne wood coatings formulated by PA with 4.5% MAA dosage was low to 33 g/L.