Abstract: A large variety of opals are produced from WOLLO,Ethiopian,but the fire opal and water opal are unstable and easy to crack due to the change of temperature or moisture.Those cracks seriously affect the stability and processing performance of the opals.Therefore,the filling treatment of the fire opal and water opal from WOLLO are studied in this experiment.And then the microscopic magnification observation and specific gravity,UV fluorescence,infrared spectroscopy are also used for test and analysis of the opals before and after the filling treatment.Some identification characteristics for opals with organic filling are summarized.The absorption peaks of the infrared spectrum at 2 800-3 100 cm^-1 are the main identification characteristics to distinguish the natural opals from treated samples.And the surface,internal characteristics by filling treatment under microscope,smaller specific gravity,strong blue-white UV fluorescence and worm-like appearance at the cracks could also be used as auxiliary identification characteristics.We can conclude from the results and discussion in the experiment that the filling treatment of opals are feasible and those open cracks are easily filled.