Abstract: A method of localization by STI based on genetic algorithm is presented. This method of localization can solve the problems of traditional methods - requirement of large computation or difficulties in initial value selection. The limitations of the genetic algorithm, such as immature convergence and bad real-time property, are resolved by means of down-sampling, parallel computation, adaptive processing and so on, which makes the method effective and accurate in the localization of underwater target. This method of localization is realized on DSP with consideration of DSP's specialties. It's the combination of DSP and Genetic Algorithm that makes the method of localization by STI applicable.