The invention discloses a high-adaptability and high-performance polycarboxylic water-reducing agent, which is obtained by polymerizing a monomer a (methyl allyl polyethenoxy ether or methyl butyl polyethenoxy ether), a monomer b (acrylic acid) and a monomer c (one or a mixture of more than two of maleic anhydride, methacrylic acid, sodium methallyl sulfonate and the like) in an aqueous solution system under the action of an initiator. The prepared high-performance polycarboxylic water-reducing agent has high adaptability with cement, and also has higher adaptability with concrete aggregate, particularly concrete prepared from manufactured sand; compared with an ordinary polycarboxylic water-reducing agent, the prepared polycarboxylic water-reducing agent has the advantages that the slump flow of concrete is higher under the condition that the slump of the concrete is kept the same, and the concrete can freely flow more favorably.