A novel nondestructive measuring method for the refractive index of a transparency capillary is introduced in this paper. When a collimated light passes through a capillary filled in a standard liquid with known refractive index

the focal position is dependent mainly on the wall-material of the capillary.On the basis of the above

the position and focal length of a capillary are imaged by a lens onto a CCD chip accurately

when the capillary is filled in two different liquids with known refractive indexes

respectively.Then

the refractive index of the wall- material is obtained by measuring and calculating two positions and focal lengths separately. The measurement accuracy of refractive index is better than 0.005. The effects of measuring parameters

including inner and outer diameters of the capillary

the refractive index of satandard liquid

as well as the image depth and sensitivity of refractive index on the measuring precision are analyzed. It is shown that the thicker capillary wall is

the higher the measuring precision is

and the lower the refractive index of standand liquid is

the higher the calibrating accuracy is. The introduced method is characterized by simple equipment

easy to operation

convenient to observe and its measurement precision of refractive index can meet the requirements of general scientific research and experiments.