The invention relates to a preparation method of a linear polyolefin porous material. Polymerization monomers use olefin monomers, such as acrylates, styrene, acrylonitrile, vinyl acetate and functional monomers, in a mixed solvent composed of polyethylene glycol or a suitable solvent (or precipitant) Dissolve in medium, carry out free radical polymerization in azo and peroxy organic initiators, suitable temperature and atmosphere, but different from solution polymerization and precipitation polymerization, there is a characteristic that the polymerization reaction promotes phase separation, and finally solidifies into Block, remove polyethylene glycol, etc., to obtain a linear polyolefin porous material. The prepared polymer porous material is integrally continuous, the pore structure is an open and connected channel, the average pore diameter is in the order of micron to nanometer, and the size of the pore structure can be regulated by polyethylene glycol (PEG) and a mixed medium. Chemical modification of pores can be widely used in separation, filtration, adsorption, chelation and intelligent membrane materials in instrument analysis, water treatment, biomedicine and other industries.