Proposed and designed is a high coupling efficiency apodized one-dimensional grating coupler based on X-cut lithium niobate insulator platform. The overlay amorphous silicon is employed to enhance the coupling efficiency by combing subwavelength photonic crystal design and genetic algorithm. The optimized grating coupler exhibits a peak coupling efficiency of -1.08dB, which can be further improved up to -0.53dB by introducing a bottom metal mirror, with a 1dB bandwidth of 61nm at central wavelength of 1550nm.