The performance of polycarboxylate (PCE) superplasticizer in concrete with machine-made sand greatly depends on the adsorption behavior on stone powder, which is concerned with the lithology and specific surface area. The workability can be improved via enhancing the adsorption of PCE on stone powder. In this regard, the rheological behavior of cement paste and cement/microcline paste with conventional PCE superplasticizer and phosphate-containing PCE superplasticizer was tested. The incorporation of phosphate group can enhance the adsorption of PCE molecule on the surface of microcline, thus improving the packing density of cement/microcline mixture. The average particle separation distance increases. Therefore, the dispersing performance of PCE superplasticizer in the mixture is obviously improved. The apparent viscosity of paste is reduced. The performance of phosphate-containing superplasticizer is even better when incorporating high content of microcline.