Abstract: Coal gangue has become China and even worldwide environmental problems.Through the meticulous field research， sampling and comprehensive experimental research to Shiguai coal mining in Baotou，Inner Mongolia，it proved that the gangue belonged to kaolin rock.The Shiguai coal gangue（coal series kaolinite） after ground and 800 ℃ calcined at 2 h，it could be prepared for the high activity of metakaolin；and partial kaolin was added into cement mortar and the strength of the mortar could be improved.Preparation mechanism of metakaolin from coal gangue：Shiguai coal gangue had high silicon and rich aluminium，and calcination free silica and aluminum oxide as where its activity，the first ground after calcining and grinding of the mechanical and thermal processing composite activation process，can fully arouse the calcined coal gangue sintering activity of metakaolin.

Key words: coal gangue；Shiguai mining；coal kaolinite；metakaolin