In order to realize the industrialization of the new converter transformer， one of the important preconditions is to make matched protection scheme for the new converter transformer. The principle of differential protection for the new converter transformer is studied. Based on the analysis on the special windings wiring mode and turns ration relation of the new converter transformer， the relationship between bilateral currents of the new converter transformer are obtained， and two differential protection wiring schemes are thus proposed. The differential protection principle for the new converter transformers is tested under all operation conditions so as to compare the protection action characteristics. The results show that the differential protection scheme composed by subtraction of each two phase currents is better than the differential protection scheme based on the phase currents of primary side. The results can provide theoretical guide to the differential protection wiring scheme for the new converter transformer for actual engineering applications.