[Objective] This study aims to explore the regulation of exogenous nitric oxide (NO) on the growth and quality of Leonurus japonicus under drought stress, in order to provide theoretical basis for drought tolerance cultivation and quality improvement in L. japonicus. [Methods] The 100 μmol/L sodium nitroprusside (SNP; a NO donor) was used as pretreatment, and 10%, 20%, and 30% polyethylene glycol (PEG)-6000 was used to simulate different degrees of drought stress. The effect of exogenous NO on seed germination, seedling growth, and the content of medicinal components in L. japonicus seedlings under drought stress was analyzed. [Results] (1) The seed germination under 10% and 20% PEG treatment was significantly improved by the regulation of amylase activity through exogenous NO. (2) Exogenous NO could markedly mitigate the inhibition of the growth of L. japonicus seedlings under drought stress. Above observation was likely attributable to the reduction in malondialdehyde and hydrogen peroxide levels, thereby decreasing oxidative damage. (3) The analysis for medicinal components showed that, exogenous NO significantly enhanced leonurine hydrochloride content, stachydrine hydrochloride content, and flavonoid biosynthesis in L. japonicus seedlings under drought stress. [Conclusion] Exogenous application of NO could alleviate the seed germination and seedling growth of L. japonicus under mild and moderate drought stress, and promote the accumulation of medicinal components under stress.