The invention belongs to the technical field of medicine and discloses a refining method of an effective part of bitter gourd for reducing blood sugar, comprising the steps that: (1) the bitter gourd medicine liquid is prepared before decoloring and refining: the decoction sheet of the bitter gourd is dried, crushed, extracted in an recycling manner by ethanol and concentrated to gain the extract; the extract is diluted, absorbed through big-pore absorbing resin column, washed, eluted with the ethanol solution to obtain the bitter gourd medicine liquid before decoloring and refining; (2) a refining process is carried out: the ethanol eluting solution of the resin column is collected and a discoloring agent is added , the mixing solution is heated and recycled, filtered, concentrated after reducing the pressure, dried in vacuum to obtain the steroidal glucoside of the bitter gourd. The steroidal glucoside of the bitter gourd extracted by the method of the invention can be directly made into various preparations, such as troche, capsule, grain, oral liquid, tablet, suspension, pill, cataplasma and paste, etc. Compared with the traditional technique, the invention is characterized by small volume, strong resistance against moisture and high content of the effective component. Compared with a solvent extracting method, the invention does not use organic toxic solvent which volatilizes easily in the technological flow, thus, the invention has safe and reliable operation, low production cost and no pollution to the environment.