The invention discloses a manufacturing method of a duplex stainless steel chemical ship side section and belongs to the technical field of ship construction. The method includes the following steps of firstly, carbon steel outer plate secondary medium assembly construction, secondly, stainless steel inner longitudinal wall plate secondary medium assembly construction, thirdly, inner longitudinalwall plate flat straight section medium assembly construction, fourthly, deck medium assembly construction and fifthly, ship side section large assembly combination. In the method, when stainless steel inner longitudinal wall plate secondary medium assemblies are constructed, stainless steel molding beds are adopted, and carbon pollution caused by a common carbon steel material to a duplex stainless steel material can be effectively prevented; and through reasonable selection of the assembling sequence and the assembling pose, an automatic angle welding machine can be conveniently used for welding stainless steel, deformation of the duplex stainless steel is effectively reduced, the duplex stainless steel ship side section is divided into flat straight section medium assemblies and deck medium assemblies, the modes of same molding bed construction and medium assembly separate combination are used, the construction accuracy is guaranteed, and section construction efficiency is improved.