The invention discloses a search method of a power transmission section between power grid partitions. The method comprises the following steps of setting a call line of a power grid between power supply areas to be in a disconnected state; setting a line with a specified voltage level to be in an open circuit state; carrying out topology search on each area of the power grid to form each electrical island, and determining each electrical island of a line node containing the specified voltage level to be one partition; calculating the number of nodes included in each power grid partition, setting a partition node number threshold, and determining, and according to the threshold, determining whether all the nodes of the electric island are merged to the connected electrical island; and searching a power sending line and an incoming line of the power grid partition, and determining the power transmission section of the power grid partition according to a judgment condition of the power transmission section. The problem of a power transmission section demand existing in an automatic identification system is solved.