An internal foaming rubber of a dual density Goodyear outsole and a preparation method thereof. The internal foaming rubber of a dual density Goodyear outsole is prepared by the method of: weighing 800-1000 weight parts of natural rubber, 500-700 weight parts of styrene butadiene rubber, 1100-1300 weight parts of reclaimed rubber, 50-70 weight parts of activated zinc oxide, 40-50 weight parts of stearic acid, 20-30 weight parts of antioxidant, 700-800 weight parts of N330 carbon black, 400-500 weight parts of light calcium carbonate, 80-120 weight parts of machine oil, 200-250 weight parts of phenolic resins, 15-20 weight parts of vulcanizing agent, 35-45 weight parts of promoter, 10-20 weight parts of foaming agent and 10-20 weight parts of foaming agent; plasticating the natural rubber, mixing the natural rubber with styrene butadiene rubber and reclaimed rubber, uniformly dispersing and storing for one day; adding the rubber compound into an internal mixer, adding carbon black, light calcium carbonate and phenolic resins, pressing a ram piston, lifting the ram piston 40-100s later; adding activated zinc oxide, stearic acid, antioxidant, foaming agent and machine oil, pressing the ram piston and discharging the materials after load stabilization of the internal mixer; adding the obtained materials into an open mill, pulling out three channels and adding promoter, vulcanizing agent and urea; making five triangle packages after rubber mixing, removing a sheet and hanging; detecting; putting qualified mixed stock in the open mill for thermal aging and processing the mixed stock into a required prescribed shape.