In Traditional Chinese Medicine (TCM), Liu Ji Nu belongs to the 'Herbs that invigorate the Blood' category. Like the name indicates these herbs tend to stimulate the Blood flow. In TCM they're used to help the circulation of Blood in cardiovascular conditions or menstrual irregularities as well as to treat acute pains caused by Blood Stagnation. They can also be used to treat Blood Stagnation when it causes certain tumors, cysts and hardened clots.
Furthermore Liu Ji Nu is Warm in nature. This means that Liu Ji Nu tends to help people who have too much 'Cold' in their body, although with less effect than a plant that would be Hot in nature. Balance between Yin and Yang is a key health concept in TCM. Those who have too much Cold in their body are said to either have a Yin Excess (because Yin is Cold in nature) or a Yang Deficiency (Yang is Hot in Nature). Depending on your condition Liu Ji Nu can help restore a harmonious balance between Yin and Yang.
Liu Ji Nu also tastes Bitter. The so-called 'Five Phases' theory in Chinese Medicine states that the taste of TCM ingredients is a key determinant of their action in the body. Bitter ingredients like Liu Ji Nu tends to have a cleansing action on the body by clearing Heat, drying Dampness and promoting elimination via urination or bowel movements.
The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such Liu Ji Nu is thought to target the Spleen and the Heart. In TCM the Spleen assists with digestion, Blood coagulation and Fluids metabolism in the body. In addition to regulating Blood flow, the Heart is believed to be the store of the 'Mind' which basically refers to someone's vitality.