The invention relates to a dynamic section control method based on a power flow transfer ratio. The method comprises the following steps: switching off each branch one by one, detecting the load rates of branches which are not switched off gradually, judging whether or not the load rates of certain branches in the branches which are not switched off are greater than a preset load rate threshold value, and if so, selecting corresponding switch-off branches as key branches; calculating the power flow transfer ratio of each branch with a direct-current power flow algorithm; judging whether or not the power flow transfer ratios of the branches are greater than a preset power flow transfer ratio threshold value, if so, selecting the branches for serving as strong correlation branches, wherein the strong correlation branches and the key branches construct a power transmission section; acquiring a dynamic ultimate expression of the power transmission section according to the power flow transfer ratios, load fluctuating power, rated active power and a generator switchable amount or a load switchable amount; and controlling section power flow according to a power transmission distribution factor and the dynamic ultimate expression of the power transmission section. The dynamic section control method is suitable for the complex change of a power grid running way, accurate in results, small in calculation amount, convenient and practical.