The invention relates to medium-carbon alloy cast steel shots and a manufacturing method thereof. Each medium-carbon alloy cast steel shot comprises the following chemical components in percentage by mass: 0.35 to 0.45 percent of carbon, 0 to 0.2 silicon, 0.45 to 0.5 percent of manganese, 0.8 to 1.2 percent of chrome, 0 to 0.015 percent of sulfur, 0 to 0.020 percent of phosphor and the balance of iron and inevitable impurities. The manufacturing process comprises the following steps of: mixing and smelting, namely, smelting the raw material composition mixed proportionally into liquid steel, pouring the liquid steel into a tundish and performing deoxygenation by adopting an deoxidant; preparing shots by a centrifugally forming method, namely, pouring deoxygenized liquid steel into a centrifugal disc which rotates at a high speed, throwing out the liquid steel under the action of a centrifugal force to make the liquid steel fall into a cooling water pool, and taking the liquid steel out and drying the cooled steel to obtain formed cast steel shots; and performing heat treatment, namely, heating the formed cast steel shots until the temperature reaches 860 to 880 DEG C, performing cold quenching after keeping the temperature for 20 to 40 minutes, tempering for 40 to 80 minutes at the temperature of between 350 and 500 DEG C, and after tempering, cooling rapidly by a steel plate vibrating screen water cooling method to produce the medium-carbon alloy cast steel shots. The medium-carbon alloy cast steel shots and the manufacturing method thereof have the advantages of guaranteeing the high rigidity of the steel shots, avoiding crack generated in the centrifugally forming process and the heating tempering process, improving the toughness and the like.