The article presents a water-wall tube panels simulation technique that uses finite element method as well as the power boiler water-wall structure design optimization method. Results of the proposed method verification and its application to the design of boilers of different capacities are discussed. The technique is to replace water-wall tube panels with equivalent plates. Replacement plates’ parameters calculation is reported, panels one-way heating metering is described. Optimization of the water-wall structure design is carried out in two stages: at the first stage, water-wall tube panels are replaced with orthotropic plates; at the second stage, sub-simulation with solid models is used to identify problem areas of the design. Solid-state models of the problem areas get connected to the orthotropic plates at calculated boundary conditions. The described approach improves accuracy of the simulation results and significantly reduces the models complexity and its computation time. The proposed simulation and optimization method has been tested and successfully applied to design power steam boilers with steam generating capacity of 500, 1030 and 1900 tons of steam per hour. As a result, while maintaining the specified reliability and durability, significant reduction of metal content in boiler structure is achieved.