Introduction  In this paper， the structural design scheme of the main plant of 9H class gas-steam combined cycle unit is studied， and the best arrangement of main plant is found out.

  Method  Through improvement of structure type， calculation method and design parameters were discussed and analyzed technology， investment， construction period and construction organization in detail.

  Result  Based on research results， both reinforced concrete and steel structure are acceptable. But reinforced concrete structure with steel roof truss is recommended because of economic factors.

  Conclusion  It is recommended that the main plant use reinforced concrete structure and the main bearing structure of the main plant building surface adopt steel roof truss.