The invention relates to a porous composite material, in particular, a layered dual metal hydroxides/cellulose porous composite material and a preparation method thereof. Cellulose, layered dual metalhydroxides, and meerschaum/glass fibers are taken as raw materials, the raw materials are directly blended and then frozen-thawed at a temperature of -35 to -25 DEG C, the layered dual metal hydroxides are evenly dispersed in a cellulose solution, meerschaum (or glass fibers) is optionally added; the mixed solution is painted, gelated, and freeze-dried to prepare the layered dual metal hydroxides/cellulose porous composite material; (or after gelation, the mixed solution is processed by a supercritical drying treatment or an electrostatic spinning and moulding technology to obtain the composite material), and the composite material is in a sponge shape, a membrane shape, or a nonwoven cloth state, and the mechanical properties of the composite material are adjustable. The preparation is simple, little pollution is generated, the raw materials are all environmentally friendly, the mechanical properties can be adjusted in a certain range, and the composite material can be flexible or stiff therefore.