Abstract: The disposal of used tires causes many environmental problems, and the crushed rubber powder can replace fine aggregate in building mortar. The content and particle size of rubber aggregate in mortar are the main factors affecting the strength of rubber concrete. Alkali-activated slag can replace ordinary Portland cement and improve the environmental friendliness of mortar. The influence of multi-factor coupling on the compressive properties of rubber aggregate mortar was studied. By testing the compressive strength of mortar, significance analysis of the test results was completed and the multivariate nonlinear regression model was established. The microscopic pore measurement and SEM test of mortar samples were carried out to explore the degradation mechanism of rubber aggregate on the compressive strength of mortar. The results show that the increase of rubber aggregate content in mortar will cause the decrease of compressive strength of mortar. Compared with the control group, the average compressive strength of alkali activated mortar decreases by 49.93% and the silicate mortar decreases by 66.62% under 40vol% aggregate replacement rate. Under the high alkaline environment of alkali-activated mortar, the average compressive strength of mortar using 0.38 mm rubber aggregate is 69.65% of the control group, which is the optimal value in the test group. In the low alkaline environment of silicate mortar, with the decrease of rubber aggregate size, the average compressive strength of mortar decreased from 61.46% of the control group to 37.98%.