The invention relates to a small circuit breaker for plug-in installation, which consists of two small single-pole circuit breakers and a wiring base, wherein the two small single-pole circuit breakers are in assembly connection in parallel through rivets; the upper part and the lower part of the back lateral surface of any small single-pole circuit breaker are provided with a binding post respectively; the upper part and the lower part of the wiring base are provided with two wiring sleeves at intervals respectively; the binding posts are in nested connection with one wiring sleeve respectively; the wiring base is arranged on a clamping rail of a distribution box; and an upper wiring board and a lower wiring board of the wiring base are connected with a power-supply side connecting wire and a load side connecting wire respectively. When an application circuit generate faults and the small circuit breaker needs to be replaced, the two small parallel single-pole circuit breakers are pulled out of the wiring base directly without cutting off power supply, and after being maintained or replaced, the small single-pole circuit breakers are plugged in the wiring base again; and after the small single-pole circuit breakers leave away the wiring base, handles of the two small single-pole circuit breakers are locked by utilizing a lever mechanism so as to prevent the false operation ofthe handles and power operation.