Abstract: In this paper the modifying technology of vegetable tannin in place of phenol partially to produce aminosulfonic acid-based superplasticizer was studied.The result indicates that the better modified technological conditions are as follow:mass percent of vegetable tannin to total vegetable tannin and phenol is between (25%)-(37.5%),reaction time is about (3 h),temperature is about (90℃),and pH is between 9.0-11.0.The modified product has a little worse dispersing capability than that of(unmodified) product,but its slump loss is a little bigger.When the dosage in cement is (0.5%),and the water-cement ratio is(0.28 :1),the fluidity of cement paste added modified and unmodified product is 240 and (252 mm),respectively.