The utility model provides an emulation current transformer, includes switching circuit board and mutual -inductor model, is equipped with primary current output interface, primary current input interface, electric current source input interface and secondary current output interface on the switching circuit board, be equipped with more branch between primary current output interface and the primary current input interface, wherein at least two are equipped with a relay on the road respectively, between switching circuit board and the mutual -inductor model, the primary current output interface of switching circuit board and mutual -inductor model socket are between I, the primary current input interface and the mutual -inductor model socket of switching circuit board link to each other with many wires between II, the secondary current output interface and the mutual -inductor model socket of switching circuit board link to each other with 2 wires between III. The utility model provides an emulation current transformer can realize that the heavy current becomes the basic function of undercurrent in proportion, avoids the high voltage, guarantees safely and can automatic change thetransformation ratio, reduces volume, weight, cost.