The invention discloses a small volume breaker, including a first breaker unit (31) and a second breaker unit (32) arranged in a stacked manner. A housing of the first breaker unit (31) is provided with a first projection portion (33) and a first concave portion (34). A housing of the second breaker unit (32) is provided with a second concave portion (35) and a second projection portion (36). Thefirst projection portion (33) and the second concave portion (35) are plugged in a matched manner. The first concave portion (34) and the second projection portion (36) are plugged in a matched manner. The small volume breaker is small in volume, length is not longer than 80 mm, monopole modulus thickness is 9 mm, and thickness of only coil part is 12 mm. However, after poles are spliced, breakercoil projection portions would be assembled in the concave portion of another pole. Total width is 9 mm x (the number of poles) + 3 mm. The breaker saves space, and saves materials by more than 40%. The breaker is advantaged by high operation reliability, simple structure, and low cost.