In the Han-Tang period, there was a close relationship between the produce and development of the Grain Transport and the military activetity. The Grain Transport by water had a very important function.The Han-Tang government utilized the Grain Transport by water to promopt unified war. The unified power utilized the Grain Transport by water to transport military provition and soliders when it occupy the advantage . Digging through a canal was a effective strategy to prompt combating . Political powers would build up the grain transport system in the vulnerable area to carry out the positive battle of attrition . In the fission time , the canals built by previous dynasty can be used by different political powers to unite China again .The Grain Transport by wayer influenced the military affairs in the frontier greatly. Military center of gravity in the frontier was one of profitable targets of the Grain Transport by water. Northwestern region was the military center of gravity in the frontier in the Han-tang period. Howerver, it moved east in the Sui dynasty and the Tang dynasty . The Grain Transportation and the grain transport syetem changed correspondingly .The military geography effected on the the Grain Transport by water profoundly . On the other hand , the Grain transport by water strongthen and changed some characters of the military geography .The relationship between military geography and the Grain Transport changed and developed according to the military center of gravity and region relations.The water transport warehouses are important parts of the the grain transport system. Some were military warehouses, even military foothold . Many were warehouses of states and counties , or transportation warehouse ,which stored and transported for military activity, too. Government made use of the warehouses to consolidate the political and military authority , and to enhance the unification . When government select the location of water transport warehouses , they considered and inspected not only economic and transporting condition but also military strategic need .The Grain Transport by water was the lifeline of the unification from the military angle.