The stable gel suspensions (SGS) were prepared by using sodium alginate (SA) and fly ash (FA) to form a wide network structure in solution, and the suspension mechanism was analyzed. According to the mechanism of suspension, a large number of SA molecules gathered on the surface of FA particles due to chelation, which made FA particles evenly dispersed in the solution. Then the colloidal particle-stabilized foam (CPSF) was prepared by a certain amount of the SGS and aqueous foam. The effects of different foam-expansion ratios on the half-life time and viscosity of the CPSF were investigated. The foam stability showed that the half-life time of the CPSF changed significantly with the increase of the foam-expansion ratio. Considering a foam half-life time >20 h, the effective foam-expansion ratio range of CPSF was determined as 4.51-7.06. A higher foam-expansion ratio resulted in a poorer viscosity of the foaming solution. Meanwhile, the shear-thinning characteristics were more significant. The results of fire-extinguishing experiments and accelerated oxidation experiments indicated that the CPSF could be well-attached to the surface of coal particles, effectively increase the CPT of coal samples, delay the appearance time of CO significantly, reduce the generation of CO rapidly, and show good inhibition performance.