The invention provides a flyash geopolymer based porous material and a preparation process thereof. The porous material comprises the following components in parts by weight: 60-100 parts of flyash, 40-70 parts of alkali activator, 0-40 parts of admixtures, 0-5 parts of glass fibers, 2-8 parts of physical foaming agents and 0-0.8 part of chemical activators, wherein the alkali activator is alkaline mixed liquor containing various ions and comprises industrial water glass, sodium hydroxide, water, polyethylene glycol and sodium phosphate; the admixtures refer to levigated metakaolin, silicon micropowder and calcined coal gangue; the physical foaming agents include expired shampoo, an anionic surfactant sodium dodecyl sulfate (SDS), fatty alcohol polyoxyethylene ether sodium sulfate (AES) and disodium fatty alcohol polyoxyethylene ether monosulfosuccinate (AESS); the chemical foaming agents include aluminium powder, hydrogen peroxide, and the like. The porous material has adjustable volume density, fine and uniform pore diameter, low heat conductivity, high strength, the same life as buildings and good fireproof performance.