Taking the gross-pitaevskii（G-P） mean-field energy functional of Bose condensed gas as the objective function, we study the properties of Bose condensed gas in 1D optical lattice system by using the genetic algorithm, and present a new method to find the ground-state wave function of the system. Through the optimized computation, the currently commonly used Thomas-Fermi approximation and Gaussian approximation model are revised and discussed, and the optimal ground state wave function is given.