Abstract: In order to effectively treat power plant waste fly ash and rice husk ash and realize the recycling of solid waste resources, the cement backfill is prepared by using fly ash and rice husk ash as raw materials to achieve the purpose of solid waste treatment. In this paper, uniaxial compressive test, slump test and electron microscope scanning are used to systematically analyze the change characteristics of the compressive strength and slump of the backfill, and the evolution law of the microstructure of the fly ash-rice husk ash backfill is verified, and the ratio parameters of the backfill are optimized. The results show that adding fly ash can improve the slump of slurry, but the increase of rice husk ash, rice straw fiber and activator content will lead to a downward trend of slump. With the increase of fly ash content, the compressive strength of backfill firstly increases and then decreases, and the reasonable content range is about 10%. The increase of rice husk ash, rice straw fiber and activator content can improve the compressive strength of the backfill. When the content of fly ash, rice husk ash, rice straw fiber and activator is 20%, 9%, 0.4% and 2.5%, respectively, the strength and slump of cement backfill can meet the requirements of mine filling, and the cost of filling material per unit volume is 72.88 yuan/m³, which can be used as the best material ratio scheme in this test. The extension of maintenance age can significantly reduce the number and scale of internal void structures in the sample, which is conducive to the formation of a more stable network support system inside the fly ash-rice husk ash backfill, thereby enhancing the macroscopic mechanical properties of the sample. The research results can provide theoretical guidance and scientific basis for the regeneration and utilization of fly ash and rice husk ash and the design of filling material ratio parameters.