The invention relates to a circuit breaker embedded with a low-voltage side electronic current transformer, which comprises an upper outgoing line board, an arc extinguish chamber, a transformer chamber and a lower outgoing line board arranged in the direction of a center penetrating bus in turn, and an insulating tension pole connected with the center penetrating bus; the low-voltage side electronic current transformer is arranged in the transformer chamber and comprises a Rogowski coil, a low-power coil and an insulating support seat coaxially sleeved on the center penetrating bus; an insulating ground pipe is arranged between the insulating support seat and the ground; and the outgoing lines of the Rogowski coil and the low-power coil pass through the insulating ground pipe to connect a low-voltage side signal processing circuit and a power circuit thereof. Because the Rogowski coil does not have the saturation problem, the frequency band range is wide, the fault current can be precisely measured, and the sensitivity and reliability of a protection device are improved; in addition, the electronic current transformer is small in volume, and a large number of iron core materials and non-ferrous metals are saved.