Abstract: In this study, the influence of calcium aluminate cement on the properties of fly ash based geopolymer was analysed. Calcium aluminate cement was used to replace fly ash, and the content was 0%, 2%, 4%, 8% and 12%, respectively. SEM, XRD, FTIR and TG were used to explore the micro-mechanism of geopolymer with calcium aluminate cement; fluidity test, setting time and compressive strength test were carried out to analyze the macro-performance of geopolymer with calcium aluminate cement. The results show that when the content of calcium aluminate cement increases from 0% to 12%, the content of C-S-H gel increases from 2.16% to 8.1%, and the content of aluminium-rich gel grows from 55.22% to 74.6%. Increasing the content of calcium aluminate cement, the fluidity decreases from 22.4 cm to 21.5 cm, initial setting time decreases from 622 min to 106 min, final setting time drops from 740 min to 125 min, and the compressive strength increases from 27.7 MPa to 70.78 MPa. Therefore, adding calcium aluminate cement is beneficial to the formation of more C-S-H gel and aluminum rich gel, and C-S-H gel has a greater generation rate, which reduces the working performance and improves the compressive strength of geopolymer, which enriches the method to improve the properties of geopolymer.