As the research objects of geology, terrain, landforms, engineering geology and geological disasters create lots of battle miracle in traditional contact war. But the modern war's characteristic is global precision attack, no precision boundary between frontline and back, and unimportant role of ground force. This article discuss the function of geological factors in modern war and provide thoughts for application of geology in modern war. Methods:Studying with the characteristics of modern war, the requirements for military geology, evolution stage of war and geological application history, utilizing military thought, we discuss the function of geological body's mechanical properties, geochemistry, physical geography and geological hazard in modern war. The function mainly include certain services for optimization of precise strike and defence priorities, the weapon choice for striking ground fortifications, target detections and the choice of targets, the environment construction of ocean wars and the war estimation, the layout of ground temporary maneuver route and location selection of fortification. We discuss the problem of military geological survey's key region, methods and means, choice of scale, and the workflow, achievement expression based on regional geology, engineering geology, hydrogeology, hazardous geology, geophysical survey, analyze the development and research emphasis of future military geology.Results:Geology can play important role in military, such as ocean battlefield environment, optimal selection of precision attack ground targets, target investigation and precision guidance, the layout of ground temporary maneuver route and location selection of fortification, weapon scientific selection for underground fixed installation, the war environment estimation. Conclusions: Modern war need military geology. Military can solve some problems in modern war. Investigation and collection of military information, classification investigation of military target should be paid more attention.