Integrally geared centrifugal compressors have been widely used in industry especially. Reliable design, good performance, low noise, no resonant frequencies in the operating range and cost effective machining and casting parts are the goals of the design. Computational Fluid Dynamics (CFD) tools have been widely used to optimize the impeller, diffuser and volute designs. Many design considerations are useful for compressor preliminary parameter selections and compressor package designs. In this paper, the detailed development and design of a integrally geared centrifugal compressor are discussed. Some initial design considerations for compressor configureuration, power distribution for each stage, and possible field application issues are discussed in details. The aerodynamic and structural optimization using CFD and Finite Element Analysis (FEA) are performed to obtain a high efficiency and wide operating range compressor with robust operation. The new compressor development process addressed in this paper provides the basic design guidance for future new integrally geared compressor development.