The invention relates to a method for carrying out adaptive discriminating on the polarity of a CT (current transformer) of a new line in a distribution network, and the method comprises the following steps: marking out a differential area comprising the CT of the new line in the distribution network; then, on the basis of taking the polarities of CTs of lines (except for the new line) in the differential area as known quantities, discriminating the polarity of the CT of the new line by way of differential protection calculation. By using the method disclosed by the invention, the problems that a manual verification mode is long in consumed time and inconvenient to use are solved.