The invention relates to a method for directly synthesizing a pure 
solid high-performance polycarboxylate water-
reducer in one step, belonging to the field of water-reducers. According to the method, the pure 
solid high-performance polycarboxylate water-
reducer is prepared by taking an acrylic compound and unsaturated 
polyoxyethylene ether as 
polymerization reaction monomers, adding a molecular weight 
regulator and carrying out free-
radical polymerization reaction under the action of an initiator and under a 
solvent-free environment. The method disclosed by the invention is strong in 
controllability, high in 
polymerization degree, low in cost, environment-friendly and 
pollution-free, achieves the purpose of preparing the absolutely 
anhydrous pure 
solid polycarboxylate water-
reducer by 
bulk polymerization, not only has the fluidity and holding property of 
cement paste, 
cement adaptability and concrete application performance which are similar to those of a polycarboxylate water-reducer prepared from a common solution by 
polymerization and can be prepared into any concentration of solution according to actual demands as the pure solid high-performance polycarboxylate water-reducer prepared by direct polymerization is an 
anhydrous pure solid, but also is free of postprocessing working procedures, such as heat 
drying or 
solvent separation and is more convenient to transport, saved in transport cost and favorable in market competitiveness and application prospect.