The invention relates to wide-temperature-range low-loss Mn-Zn ferrite specially used for a solar energy inverter, and a preparation method thereof. The Mn-Zn ferrite comprises main components of: 53.5mol%-54.5mol% of iron oxide calculated according to Fe2O3, 8.0mol%-10.0mol% of zinc oxide calculated according to ZnO, and balance of mangano-manganic oxide. The Mn-Zn ferrite also comprises minor components of, by weight: 0.03-0.04% of CaCO3, 0.005-0.01% of Nb2O5, 0.01-0.03% of V2O5, and 0.03-0.2% of Co2O3, calculated according to standard substances of CaCO3, Nb2O5, V2O5, and Co2O3. The Mn-Zn ferrite is prepared with an oxide method, and is sintered under an elevator furnace densification condition. The obtained product has relatively high initial magnetic permeability mui, and low power loss Pcv. With the Mn-Zn ferrite, the loss under a high-frequency transformer operation status is reduced, and the efficiency of the transformer is improved. With the Mn-Zn ferrite, miniature inverterscan be produced with high frequency, small size, and intelligence. Also, a requirement of efficiency improving under a condition of illumination variation can be satisfied. The product is advantaged in high reliability and good stability. With the product, a miniature inverter can be used in environments with large temperature variations, such as deserts and islands.