In the high-power laser facility， control of the surface deformation of the large-aperture KDP crystal is the key factor to reduce the frequency-conversion efficiency. To improve the assembling quality of the KDP crystal， a point-supporting process method is proposed for minimizing the assembly deformation. First， a genetic algorithm is used to optimize the support points and their distribution scheme. Second， the finite-element method is used to optimize the assembling preload. Finally， mounting optimization design process experiments are conducted to evaluate the surface deformation and the frequency-doubling conversion efficiency. The experimental results indicate that the proposed method is effective for minimizing the assembling deformation of the KDP crystal； the measured PV value is 6.51 μm， and the measured conversion efficiency of second-harmonic generation reaches 72.6% with excellent assembling repeatability. This result significantly improves the frequency-doubling efficiency and the quality of the far-field spot and has been widely used and promoted in engineering.