The adsorption of two shrinkage reducing admixtures(SRAs) on the surface of solid particles, such as cement clinker, slag and fly ash were investigated. Besides, the effect of SRA on surface tension and evaporation rate of water solution and simulated pore solution(SPS) were researched as well. The results indicate that the average adsorption rate of SRA on the surface of solid particles is less than 10%, so more than 90% of SRA remains in solution. The SRAs can significantly reduce the surface tension and evaporation of water solution and SPS. The action course and mechanism of SRA can be considered as the fact that the shrinkage reduction of cement based materials is resulted from the dissolution of SRA in the pore solution leading to significant reduction of surface tension of pore solution. Meanwhile, the SRA lowers the evaporation rate of the solution. These two effects may be the main causes of shrinkage reduction of cement based materials.