Coal storage is adequate in China, building up thermal generator set exerts short construction period and low cost, 73% of thermal power generating units used out of 800 million units in China. The coal storage is to guarantee the normal operation of generating units, in order to ensure the stable operation of socio-economic importance. Some of the previous papers are also involved in the past to the genet coal storage issues, but most of them are in power enterprise perspective, with method of using the stored power enterprises maximize the benefits of the problem, this is the stand point of power grid enterprises to study the coal storage reserve margin for the economic stability of the whole society to run normally. This paper uses optimal control of differential equations for this problem and study carefully the mathematical derivation and calculation, finally prove that the economic performance needs proper functioning of the coal reserve margin indicators, and would be helpful for power system and the administrative department of government related management system, would also help power companies avoid coal supply risk in advance to some extents.ximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.