The invention provides a polycarboxylic-acid concrete efficient water reducer with an amide/imide structure. The polycarboxylic-acid water reducer prepared by employing the method has the advantages of being simple and easily controllable in technological operation, safe and environment-friendly in preparation synthesis, low in cost, energy-saving, consumption-reducing, substantial in water-reducing dispersing effect, high in storage stability, capable of reducing slurry viscosity under the condition of a low water-binder ratio, and the like. The polycarboxylic-acid water reducer has relatively good adaptability to different kinds of cement under the condition of low doping amount or low water-cement ratio, and helps to solve the problems that the raw material preparation cost of amide/imide type polycarboxylic acids is high, preparation conditions are severe and difficult to control, and the like.