Abstract: The large-scale application of coal gasification technology produces a large amount of coal gasification slag that is difficult to handle. As a kind of coal gasification ash rich in aluminosilicate minerals, coal gasification coarse slag has the characteristics of pozzolanic activity and low carbon content, and can be used as supplementary cementitious material. In order to explore the activity characteristics of coal gasification coarse slag under different modification effects and its influence mechanism on the hydration and hardening performance of cement, this paper analyzed the hydration exotherm, compressive strength, composition and structure of hydration products of the blended cement paste mixed with modified gasification slag, which were compared from macroscopic and microscopic perspectives. The results show that the addition and modification of diethanol monoisopropanolamine (DEIPA) can significantly improve the grinding efficiency and potential hydration activity of gasification coarse slag, effectively reduce the extension of hydration induction period and reduce the retarding effect of gasification coarse slag on cement hydration. The addition order of DEIPA has little effect on the hydration hardening properties of blended cement. The coal gasification coarse slag modified by chemical and physical coordination can be used as the admixture of Portland cement and concrete, and the mechanical properties of blended cement can be improved under the appropriate dosage (10 %).