The utility model relates to a three -phase is tank type circuit breaker altogether and support piece thereof to solve among the prior art three -phase altogether the three -phase explosion chamber in the tank type circuit breaker fix in the circuit breaker barrel and the problem that the circuit breaker product structure that causes is complicated, assembly efficiency hangs down through three insulating parts. For solving this technical problem, the utility model discloses a three -phase altogether the tank type circuit breaker include support piece body that insulating material made, set firmly in explosion chamber mounting structure and barrel connection structure on the support piece body link firmly the three -phase explosion chamber in the circuit breaker barrel with a support piece, and the part of greatly having simplified the circuit breaker product constitutes, have improved the assembly speed of circuit breaker product.