The invention discloses a straight-through current transformer which comprises the components of a first annular magnetic core, a second annular magnetic core, a primary current line, a secondary current line and a processing circuit. The primary current line winds the first annular magnetic core and the second annular magnetic core. The secondary current line penetrates through the centers of the first annular magnetic core and the second annular magnetic core. The processing circuit comprises a sampling signal conversion circuit and an amplifying circuit. The input end of the sampling signal conversion circuit is connected with a sampling winding. The sampling winding winds the first annular magnetic core. The output end of the sampling signal conversion circuit is connected with the input end of the amplifying circuit. The output end of the amplifying circuit is connected with an output winding. The output winding winds the second annular magnetic core. The straight-through current transformer realizes a relatively large current output range and a relatively large load range. Only one current circuit is required, and multiple complicated current circuits are prevented. Dynamic compensation for the secondary current line is realized through the sampling winding, the processing circuit and the output winding.