The invention discloses a manganese series composite pellet and a preparation method thereof. The manganese series composite pellet comprises the following components by weight percent: 26.2% of manganese, 3.79% of iron, 0.13% of phosphorus, 5.74% of silicon dioxide, 25.08% of calcium oxide and 9.5% of magnesium oxide. The alkalinity of the manganese series composite pellet is 6.02 and the compressive strength is 35-45MPa. According to the embodiment of the invention, by increasing the alkalinity of the manganese series composite pellet, the dosage of lime can be reduced, the charged ore grade can be increased, the manganese content of the slag can be reduced, the recovery rate of manganese can be increased and the power consumption can be reduced.