Relating to the technical field of medicine, the invention provides a pharmaceutical composition for treating simple obesity and a preparation method thereof. The pharmaceutical composition comprisesthe following raw materials: radix bupleuri, radix paeoniae alba, cassia twigs, allium macrostemon, rhizoma atractylodis, rhizoma atractylodis macrocephalae, fructus aurantii immaturus, mangnolia officinalis, pericarpium citri reticulatae, poria cocos, polyporus umbellatus, rhizoma alismatis, rhizoma coptidis, red yeast rice, hawthorn, chicken's gizzard-membrane, roasted astragalus membranaceus, roasted semen brassicae, fructus perillae, roasted semen raphani, fructus trichosanthis, honey-fried licorice root, ginger, jujube, salvia miltiorrhiza and cortex moutan. The prepared pharmaceutical composition is quick in effect and good in curative effect, can reduce weight and relieve symptoms, achieves the purpose of overall and systematic treatment, and can prevent and treat diabetes, dyslipidemia, cardiovascular diseases and other complications.