The test method of cement paste fluidity is adopted. The test of cement pastes fluidity was made in which two types of polycarboxylic acids superplasticizers were added. The test results show that a great increase of carboxyl and a slight increase of sulfonic groups in molecule can increase adsorption points and this enhances adsorptive ability and lowers the concentration of superplasticizer in aqueous phase, thus, the dispersion ability decreases; a significant decrease of hydroxyl groups accelerates hydration process comparatively making the adsorption process easier; the positive effect of the great increase of carboxyl (increase of absolute Zeta potential and retardation effect) is smaller than the negative effect(increase of adsorption point).