Lithium (Li) dendrite growth seriously hinders the practical application of Li metal batteries. Here, we report molecular amidinothiourea (ATU) as a new electrolyte additive to regulate Li stripping/plating behaviors of Li metal anodes. The molecular ATU in the electrolyte can act as a shielding layer on the Li metal surface to suppress the decomposition of electrolytes as verified by XPS and adsorption energy calculation, which improves the electrochemical reversibility of the Li plating/stripping behaviors and inhibits lithium dendrite growth.