Abstract：In light of computing speed，precision and reliability，the following three problems related to traditional and modern optimal methods are mainly studied： (1) the mixed genetic algorithm is presented based on the idea of coupling genetic algorithm with damping least square technique；(2) the above mixed genetic algorithm and simulated annealing-genetic algorithm are led into back analysis in geotechnical engineering early；(3) some optimal methods，such as the simplex method，damped least square technique，genetic algorithm，simulated annealing-genetic algorithm and the mixed genetic algorithm，are evaluated and compared. The studied results show that compared with the traditional optimal methods like the simplex，the modern one based on genetic algorithm is of better convergence in whole region，and compared with the common genetic algorithm，the mixed genetic algorithm and simulated annealing-genetic algorithm effectively improve searching speed，precision and reliability of genetic algorithm.
