A measuring method for the refractive index of micro-quantity liquid within a glass capillary was introduced. The capillary filled with liquid samples was used as a sphero-cylindrical lens in the system and a couple of objective lenses together with the glass capillary was used to image a micro-ruler onto a CCD imaging plane. As the image size and lateral magnification were very sensitive to the liquid filled in the capillary, the refractive index of the liquid could be exactly calculated by measuring the image-lateral magnification. The refractive indexes of four standard liquid media, pure water, ethanol, ethylene glycol and glycerin were measured, and experiments show that the accuracy of this equipment is the same as that of an Abbe refractometer(±0.000 2), and the quantity of liquid samples required by measurement is less than 0.002 mL. Moreover, the refraction indexes of a series of ethylene glycol with various concentrations were also calculated by this method and the results were compared with the values measured by the Abbe refractometer. These results demonstrate that the proposed method is characterized by micro-quantity sample required, easy operation and high measurement accuracy and it is suitable for the measurement of micro-quantity liquid quickly and exactly.