The invention belongs to the technical field of lubricating agents and discloses a lubricating agent for the combined-cold-extrusion plastic forming of a shaped charge liner and a preparation method of the lubricating agent. The lubricating agent comprises, by weight percentage, 2-8% of polyacrylamide high-molecular polymer, 1-3% of mixture of oleic acid malonate, 0.3-0.8% of sulfur phosphorus primary-secondary-alcohol-group zinc salt, 3-6% of mixture of carbamate and dialkylthiophosphoric acid derivatives containing nitrogen, 0.1-0.5% of n-octyl sulfur-based methylene, 0.2-0.5% of mixture of polydimethyl siloxane and polyether modified silicone oil, 2-5% of mixture of dialkenyl succinimide and ethyl acetate, 1-3% of mixture of magnesium naphthenate and potassium isooctanoate, 0.1-0.5% of mixture of polyaluminium ethyl siloxane and low-molecular-weight polyamide, 0.3-1.0% of butyl stearate, 1-4% of boric acid and the balance water. The lubricating agent is prepared by evenly mixing the substances above. By the lubricating agent, phenomena such as galling and cracking during the forming of the shaped charge liner can be avoided.