Controlling the wavefront distortion introduced by mechanical mounting to raise the quality of output beam in inertial confinement fusion (ICF) facility must be considered in the structure design of the large aperture Nd:glass main amplifier. A novel method of data processing between the finite element deformation results and the surface distortion of optical element was presented and compared with the traditional method. The support system of large octagonal Nd:glass is optimized with integrated optomechanical analysis method based on the new data processing interface. The transmission wavefront distortion introduced by optimal support system is less than tenth wavelength and the correlation between the wavefront distortion and the design parameters variation is little.