The invention provides a high-temperature solid state synthesis method of LiCrxMn2-XO4. The method comprises the following steps: step A, evenly mixing a lithium compound, a manganese compound and a chromium compound in a ratio of n(Li):n(Mn):n(Cr)=1.2:(2-x):x, wherein 0<=X<=0.3; step B, grinding for 0.5-2 hours on a ball grinder; step C, preheating for 4-6 hours at 300-450 DEG C in an atmosphere furnace; step D, furnace cooling, then heating-up for 700-750 DEG C and calcining for 40-72 hours; and step E, cooling to room temperature with the cooling rate of 2-7 DEG C per minute, so as to obtain a black positive electrode material. The battery positive electrode material LiCrxMn2-XO4 prepared by the invention has the advantages of high capacity, superior cycle performance and high battery safety performance, and high-current charge and discharge of the battery positive electrode material can be achieved.