The present invention relates to a medium material for eliminating arsenic pollution from groundwater, which is a granular material having an average particle diameter of 1 to 3 cm, prepared from manganese ore, meerschaum, straws, animal excrements, active sludge and active bacterium agent in a mass ratio of 1:0.2˜0.5:0.5˜1:0.2˜0.4:0.2˜0.4:0.0005˜0.002 via mixing, composting, carbonizing and crushing. The prevent invention also discloses a process for producing the above-mentioned medium material. The medium material of the present invention can eliminate multivalent arsenic from groundwater, has a long service life, and does not cause secondary pollution to groundwater.