Leonurus japonicus Houtt. has been traditionally used to treat many ailments. This study evaluated the activating blood circulation, anti-inflammatory, and diuretic effects of L. japonicus extract (LJ) and identified its phytochemicals. In this work, the phytochemicals in LJ were identified using liquid chromatography mass spectrometry. Rats were randomly assigned to three groups (n = 8): Control group was treated with saline, while the Model group (saline) and LJ group (426 mg/kg) had induced traumatic injury. All rats were treated with once by daily oral gavage for one week. The biochemical indices and protein expression were measured. Herein, 79 constituents were identified in LJ, which were effective in elevating body weight, food consumption, water intake, and urinary excretion volume, as well as in ameliorating traumatic muscle tissues in model rats. In addition, LJ prominently decreased the contents of plasma viscosity, platelet aggregation rate, thrombin time, prothrombin time, activated partial thromboplastin time, fibrinogen, thromboxane B2 (TXB2), TXB2/6-ketoprostaglandin F1α (6-keto-PGF1α), urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitor 1 (PAI-1), PAI-1/tissue-type PA (t-PA), and PAI-1/u-PA, while significantly increasing antithrombin III, 6-keto-PGF1α, and t-PA contents. Furthermore, LJ notably inhibited tumor necrosis factor alpha, interleukin 6 (IL-6), IL-8, angiotensin II, antidiuretic hormone, aldosterone, aquaporin 1 (AQP1), AQP2, and AQP3 levels, and markedly elevating IL-10 and natriuretic peptide levels. Finally, LJ markedly reduced the protein expression of AQP1, AQP2, and AQP3 compared to the model group. Collectively, LJ possessed prominent activating blood circulation, antiinflammatory, and diuretic effects, thus supporting the clinical application of L. japonicus.