Coal gangue as road engineering material can sovle the problems of energy saving and environmental protection.Experimental datas of grain size distribution,crushing value,slake durability index,expansivity,liquid limit index,plastic limit index and water absorption showed that its own characteristics are in line with the requirements of road engineering materials. There are successful cases of application of coal gangue in road constructions both here and abroad. Principal component analysis is used to identify four major factors of coal gangue applications in road construction.Put forward 5 urgent problems to be solved and give a few corresponding suggestions.