Diesel power plants come in a variety of shapes, from moveable mini-power plants installed in 40-feet standard container boxes to large capacity power plants. The world's largest diesel power plant listed in the Guinness Book of World Records is Jordan's Amman Asian power plant, which produces a total of 573 MW of electric power. It consists of 38 units of 15MW capacity, and KEPCO achieved high profitability through the power plant. If a large capacity of 40MW clsss is applied, it will be newly listed in the Guinness Book of World Records even if only 15 units are constructed. Therefore, large-scale overseas orders for diesel power plants that require large capacity are expected in the future. The purpose of this study is to derive a practical offset by performing the shaft alignment analysis for large capacity 40MW shaft system, and to infer the change of offset for larger capacity shaft system through the comparison with the 30MW shaft alignment which is the result of the previous research. As a result, the practical offset of shaft system for the 40MW diesel power generation equipment was derived through the bearing influence assessment. From the comparison of shaft alignment between 30MW and 40MW, it is considered to be a complex offset to calculate the height of the engine bearing from 50MW class.