Improvements in power electronics technology, coupling technology, high quality iron core material technology and more productive permanent magnet technology in recent years have made electrical drive systems to be more effective with respect to their reduced size, enhanced working speed and increased performance. In this paper it is focused to design highly efficient high-speed permanent magnet synchronous generator of in-runner, surface mounted, 4 poles, 2 kW and 26500 rpm for turbomachinery systems especially for turbocharger which will be used in our micro-CHP project. The criteria of selecting materials, suitable machine type, rotor structures and initial boundary conditions are explained. Electric and magnetic design of the High Speed Permanent Magnet Synchronous Generator (HSPMSG) is conducted analytically in Ansys RMxprt with parametric solutions and analyzed in Ansys Maxwell 2D&3D by finite element method (FEM) with magnetostatic and transient solutions to adjust the detailed machine shape finely and to obtain the best design parameters. The retaining sleeve is also used to provide mechanical integrity and continuity of the HSPMSG and to understand whether it is suitable for working conditions at related speeds or not. This work will also be partake of development of the related designed high speed generator.