Immature soil was used as filler to prepare immature soil based foam concrete.The properties, such as dry apparent density, compressive strength, thermal conductivity, pore structure and moisture absorption characteristic of immature soil based foam concrete were experimentally researched.The effect of silica fume on compressive strength and thermal conductivity of immature soil based foam concrete was studied as well. The experimental results indicate that the dry apparent density, compressive strength and thermal conductivity of immature soil based foam concrete decrease with increasing use level(by volume) of foam. The compressive strength and thermal insulation of immature soil based foam concrete are both improved with increasing use level(by mass) of silica fume. Moreover, the immature soil based foam concrete(60% foam) with a dry apparent density of 790kg/m3, compressive strength of 78MPa, and thermal conductivity of 0156W/(m·K) is produced to use immature soil as filler and with addition of 20% silica fume. Nanoscale pore volume of immature soil based foam concrete with 75% foam(without silica fume added) is low, and its moisture absorption ability is low also.