Add immigrants in the standard genetic algorithm can enrich the population diversity, so that SGA can better adapt to environment changes. In order to improve the space exploration search capabilities of genetic algorithm based on immigrants, inspired by primal-dual, designed Primal-Dual based Immigrants(PDI), and add PDI to SGA to solve the Dynamic Travelling Salesman Problem(DTSP). Simulation results show that PDIGA is better able to adapt to environment changes to other genetic algorithms based on immigrants.