Synthetic process of amide type polycarboxylate based superplasticizer was studied. Polyether amine（PN220） and polyacrylic acid（PAA） were used as the monomers and directly polymerized into superplasticizer. The effects of the relative molecular mass of PAA, monomer ratio, polymerization temperature and time on waterreducing rate and fluidity retention of the product were investigated through experiments. The orthogonal experiment is designed to find out the optimal synthesis technique. The performance of the product is compared with the superplasticizer which is prevailing in the market and synthesized by polyethylene glycol monomethyl ether（MPEG） and methacrylic acid. The results show that the former has excellent slump retention and it is suitable for preparation of concrete demanding outstanding slump retention.