The invention provides a method for preparing lithium lubricating grease. The method comprises the following steps of: 1) adding one third to one second of the weight of the entire base oil into a grease kettle, adding a calculated amount of monobasic acid or monobasic acid and at least one kind of dibasic acid or polybasic acid, raising the temperature, and stirring to ensure that the acid and the base oil are fully mixed; 2) raising the temperature to 40 to 80 DEG C, adding one third to one second of a calculated amount of lithium hydroxide monohydrate crystals under stirring, and fully mixing; 3) raising the temperature to 82 to 120 DEG C, and adding an aqueous solution of residual lithium hydroxide monohydrate for saponification reaction; and 4) after full saponification reaction, raising the temperature and dehydrating, continuing to raise the temperature to 200 to 220 DEG C, adding the residual base oil serving as quenching oil, reducing the temperature and cooling, adding necessary additives, homogenizing, grinding, and degassing to obtain finished lubricating grease. The method for preparing the lithium lubricating grease has the advantages of energy conservation, emission reduction and energy consumption reduction, can be used for lithium or complex lithium lubricating grease, and is particularly suitable for a process for preparing the lithium or complex lithium lubricating grease in an atmospheric kettle.