In order to explore the toughening effect of recycled rubber aggregate in geopolymer concrete, different proportion of recycled rubber aggregate (particle size 0.15~0.3 mm and 1~4 mm) was used to replace the natural aggregate in geopolymer concrete. Firstly, geopolymer cementitious material was prepared with granulated blast furnace slag powder as raw material, sodium silicate solution and NaOH as activators, and combined with natural aggregate and recycled rubber aggregate to prepare geopolymer rubber concrete. Then the mechanical properties, impact resistance and strength mechanism of geopolymer rubber concrete were studied. The results show that the compressive strength of geopolymer concrete can be improved with an increase of about 5% by adding an appropriate proportion of recycled rubber aggregate, which is related to the oxidation and degradation of recycled rubber aggregate surface in NaOH alkali environment. However, geopolymer rubber concrete is easy to fracture under indirect tensile load and bending load, and the indirect tensile strength and flexural strength are reduced by 20%~30%, which is a typical feature of geopolymer rubber concrete. In drop hammer impact test and flexural tensile impact test, recycled rubber aggregate can greatly improve the impact resistance of geopolymer concrete with the maximum increase up to more than 200%. It is due to the flexible and elastic characteristic of recycled rubber aggregate, which absorbs some impact energy. At the same time, recycled rubber aggregate also delays the process from initial cracking to failure of concrete under impact load, reduces the stress concentration of crack cracking, and improves the ductility of geopolymer concrete. Under the alkaline condition of geopolymer, the surface of rubber particles is oxidized and degraded, and the surface becomes rough and closely combines with geopolymer matrix. Under the action of NaOH, hydrophilic groups such as hydroxyl and carboxyl groups are produced on the rubber surface, which is conducive to the adhesion of hydration products on the surface of recycled rubber aggregate.