Two kinds of superplasticizer, polycarboxylate ether based superplasticizer(PCE) and polynaphthalene sulfonate based superplasticizer(PNS), and three kinds of natural limestone powder whose particle sizes are 3000 mesh(4μm), 1500 mesh(8μm) and 1250 mesh (10μm) respectively were added in Portland cement pastes with the water cement ratio of 0.3. The rheological curves of these cement pastes were determined by means of a concentric cylinder rheometer and all the rheological curves were modeled by Herschel Bulkleys equation. The results indicate that at a certain use level of superplasticizers, the rheological index n characteristic of shear thickening behavior is greater than 1, and the more the superplasticizers added, the greater the value. At the same content, the value n for the cement paste with PCE added is greater than that with PNS added. On the other hand, the limestone powder, as a replacement of some amounts of cement, can modify the intensity of shear thickening compared to plain cement pastes. When the average particle size and size distribution of the limestone powder are quite different from those of cement and the particle size in mixture becomes more and more polydisperse, the vulue n is smaller. The interaction forces among cement particles dispersed by steric repulsion are weaker than cement particles dispersed by electrostatic force, therefore, PCE are more likely to make cement particles form hydroclusters under a certain shear and cement pastes show shear thickening behavior. There is more space for flow in a polydisperse suspension compared to a monodisperse suspension, which results in lower hydrodynamic forces between the particles, hence the shear thickening behavior of the polydisperse cement paste is not markable