The invention relates to a high performance early-strength polycarboxylate water reducer and a preparation method thereof, which pertains to the water reducer field. The early-strength water reducer is prepared mainly based on graft copolymeric carboxylic polymer and compounded with a preferred early strength component; wherein, the copolymeric carboxylic polymer refers to the polymer polymerizedby methoxy polyethylene glycol acrylate and acrylic acid/methyl acrylic acid by a free radical initiator in water. The high performance early-strength polycarboxylate water reducer prepared by the invention is characterized by small doping, low alkali content, no chloride ion and no sulfate, and the like, and does not result in the corrosion and alkali aggregate reaction, and the like, of the steel bars in the concrete structure, which is helpful for guaranteeing the duration of the concrete structure. The high performance early-strength polycarboxylate water reducer manufactured by the invention can be widely applied to the construction of various concrete projects and the construction of concrete at low temperature, and is particularly suitable for the low energy consumptive production technique of concrete prefabricated parts and has promising application prospect.