The invention relates to a method for preparing a silica gel coated spinel lithium-rich lithium manganate cathode material. The method is characterized in that spinel lithium-rich lithium manganate powder is mixed with nano silica gel powder based on the weight ratio of 1:(0.001-0.02), and a precursor 2 is prepared through wet grinding and drying, wherein the chemical constitution of the spinel lithium-rich lithium manganate powder is Li[x]Mn[y]O[z]; the precursor 2 is sintered for 5-48 h at any temperature between 300 DEG C and 380 DEG C, so that silica gel coated spinel lithium-rich lithium manganate is prepared. Raw material cost is low, the heavy load discharge capacity and storage property of a sample are improved remarkably, and a sound foundation is laid for industrialization.