The improved design scheme of the Switch Network Unit (SNU) of the Experimental Advanced Superconducting Tokamak (EAST) adopts the Solid-State Circuit Breaker (SSCB) scheme composed of the parallel connection Integrated Gate-commutated Thyristors (IGCT) and the diode bridge unit for both current directions, whose rated parameters are up to ±15 kA and ±2.4 kV. The reliability operation of the whole power electronic devices of the SSCB is determined by effective heat power dissipation of semiconductor devices. In this paper, the development and thermal analysis of the water-cooled heat sink based on the double-layer Archimedes spiral fluid tube is described in detailed. In the primary design phase, the numerical simulation software based on the finite element method is used to verify the correctness of the design scheme of the water-cooled heat sink and reduce the whole design cycle. In the end, the simulation and experimental results show that the thermal resistance and pressure drop of the water-cooled heat sink meet design requirements, and also can guarantee the junction temperature of the power devices within the scope of the security under the condition of the rated current conducting work.