Abstract: Coal gasification slag is a kind of solid coal chemical waste which mainly contains aluminosilicate minerals.The gasification slag modified by mechanical grinding and chemical excitation can be used as active admixture of composite Portland cement, which can effectively reduce the carbon footprint in the production and preparation of cement building materials.In order to clarify the working performance of modified gasification slag cement fresh paste, the compatibility of gasification slag-cement binary system with superplasticizer was evaluated by studying the fluidity, ζ-potential and particle size distribution of gasification slag-cement composite paste.The results show that the coal gas slag modified by diethyl alcohol monoisopropanolamine is a kind of mesoporous material, and it has good workability when the content is not more than 30 %.Polycarboxylic acid superplasticizer is beneficial to the dispersibility and fluidity of modified gas slag cement paste, and the fresh coal gas slag cement paste mixed with polycarboxylic acid superplasticizer shows modified Bingham fluid characteristics.The experimental results have high theoretical reference value for studying the workability of gas slag-cement binary system and its compatibility with superplasticizer.