Foamed mixture lightweight soils are a mixture of cement, water, foam and soil, which are largely used in civil engineering. Soils are skeleton support structure of foamed mixture lightweight soils and can greatly impact their physical and mechanical properties. This study investigated the effect of fine fraction and sand content on the physical and mechanical properties of sand-based foamed mixture lightweight soil (FMLS), including flowability, wet density and unconfined compressive strength (UCS). Three fine fractions of sand, 13.5%, 14.5% and 15% were selected for the test. These sands replaced the cement with different proportions (0%–80%), and then mixed with the foaming agent to prepare specimens. Experimental results showed that as the sand content increases, the flowability, wet density and unconfined compressive strength all show a decrease variation. Low fine fraction can provide better properties. At the same sand content, FMLS with 13.5% fine fraction has the highest strength. In terms of the experimental results, an empirical-analytical model taking into account the effect of fine fraction and sand content to predict the unconfined compressive strength value for sand-based foamed mixture lightweight soils was proposed. The developed model can be further used for strength evaluation of foamed mixture lightweight soils.