In this paper, it was investigated that the monomer ratio, the dosage of the initiator, reaction temperature and time influenced the molecular weight of synthetic products. The research showed that the molecular weight of scale inhibitor was increased with the different synthesis conditions, which were acrylic dosage, reaction temperature and time, but the molecular weight was decreased with increasing amount of the initiator. The experiment of resistance calcium scale indicates: the molecular weight is too high or too low, the effect of scale inhibition is not ideal.