The invention discloses a foaming agent for mining filling and a preparation method of the foaming agent and belongs to the technical field of foaming agents for filling materials. The foaming agent for mining filling is prepared from components in parts by weight as follows: 20-30 parts of sodium fatty acid methyl ester sulfonate, 10-20 parts of sodium lauryl sulfate, 10-20 parts of sodium alpha-olefin sulfonate, 10-15 parts of N-lauroyl glutamic acid diester, 5-10 parts of sodium lauroyl sarcosinate, 5-10 parts of sodium lauroyl hydrolyzed silk, 5-10 parts of lauroyl diethanolamine, 5-10 parts of sodium polyacrylate, 5-10 parts of sodium hexametaphosphate, 5-10 parts of epoxy resin, 5-10 parts of guar gum, 5-10 parts of sodium alginate, 2-5 parts of potassium sorbate, 5-10 parts of a foam stabilizer and 5-10 parts of a water reducer. The foaming agent for mining filling is high in foaming speed, high in foaming force, high in foaming stability and good in hard water resistance.