The invention discloses geopolymer-based foam concrete based on straw and solid waste for light steel keel composite wall filling. The geopolymer-based foam concrete comprises, by weight, 96.2-112.1 parts of solid waste powder, 11.4-28.4 parts of alkali activator, 1.1-10.2 parts of cementitious material enhancer, 0-142.0 parts of ceramsite, 1.0-10.0 parts of surface modified straw, 3.8-9.0 parts of iron powder expansion agent, 3.2-6.0 parts of admixture and 35.8-78.6 parts of water, and 0.25-1.84 L of foam is added into the raw materials per kg or more. The geopolymer-based foam concrete is prepared by using the crop straw and the solid waste as the raw materials, the concrete is high in fluidity retention rate and great in stability, and phenomena of stratification, segregation, bleedingand collapse cannot occur. The straw is uniformly distributed, and the geopolymer-based foam concrete is good in filling performance, low in thermal conductivity, great in thermal insulation performance and especially suitable for light steel keel composite wall filling.