This paper presents design analysis and improvement of the proposed high speed hybrid excitation motor (HEM) for main spindle drive in machine tools based on experimental results obtained using prototype motor. The proposed HEM is intentionally designed using 3D-FEA for target application taking into account of practical design constraints. The basic working principle and the unique field weakening control method of the proposed HEM are studied from the prototype machine. The influence of manufacturing constraints in the design parameters of the motor are studied carefully and an improved design of the proposed HEM is analyzed. In particular, the induced voltage distortion, magnetic flux saturation in the stator pole shoe have been a major factor which has impact in the performance of the test machine, are considered in the improvement of machine design.