This work adopted 1,10-phenanthroline spectrophotometric method, complexo-metric titration and X-ray diffractometer (XRD) to investigate active state of aluminum and iron impurities in semicoke of Huadian oil shale which was calcinated at different temperatures and the influence of calcination temperature on leaching rate of impurities (Al, Fe) with acid. The results show that after calcination of semicoke of Huadian oil shale at 700-800 degrees C, iron and aluminium exist in their maximum active state and turn into materials soluble in acids, which results in their maximum leaching rate. This process is important for the removal of impurities at preparation of high-quality amorphous silica from oil shale ash.