Abstract: With the increase of coal mining depth, the deep coal seam under the action of high ground stress, high temperature and other geological environment fracture closure is not developed, low porosity, resulting in increased difficulty in water injection, water injection wetting effect is poor. In order to improve the coal seam water injection permeability, this paper uses sodium alginate as the main raw material, through molecular modification to prepare a polymer permeation enhancer. The molecular structure, crystal structure, thermal stability and fine action principle of the permeation enhancer are analyzed by Fourier infrared spectroscopy, X-ray diffraction analysis and thermogravimetric-differential thermal scanning simultaneous analysis; the adsorption process of the permeation enhancer on the coal powder surface is simulated by MS software, and the wettability and permeability of the permeation enhancer are tested. The results show that polymer permeation enhancer has the characteristics of strong wetting ability, high permeability, safety and environmental protection, and good thermal stability. After the addition of the polymer permeation enhancer, the wettability of water to coal is greatly improved, and the test group with the addition of the polymer permeation enhancer show the best permeation effect in the same time, and the shape of the permeated liquid surface is more regular; the molecules of the permeation enhancer would connect with the functional groups on the surface of coal molecules to form a stable structure, and the permeation enhancer molecules enhance the permeation ability of water to coal surface, and the water molecules in the permeation enhancer molecules. The adsorption effect of water molecules on coal molecules under the interaction of permeation enhancer molecules also increases significantly.