Abstract: A new evaluation index of compound dry separator is obtained by introducing a revising index of calorific value,which can evaluate correctly the separation performance of compound dry separators.Separation tests of raw coal with 50-0 mm size fraction by FGX-1 compound dry separator were done.Results show that the separation effect is relatively good and the values are relatively great when the exterior water content of coal is smaller than 6%,the gangue content is less than 30%,the bed amplitude is between 6-8 mm and the vibration frequency is in the range of 60-70 Hz.