Abstract: In order to improve the yield of siderophores from Synechococcus sp. PCC 7002,response surface methodology( RSM) was used to optimize the fermentation conditions. On the basis of single factor experiment,Box- Behnken RSM was employed to investigate the four factors( temperature,p H,carbon sources,nitrogen sources) on the yield of siderophores.The optimum culture conditions were as follows: the temperature was 31.7 ℃,p H was 8.28,the amount of glucose was 14.47 g / L,the amount of NH4 Cl was 0.19 g / L.Under these conditions the relative amount of siderophores from Synechococcus sp.PCC 7002 was 95.42% after 15 days fermentation while the other group without optimizing was just 64.53%.The relative amount of siderophores was increased by 47.87% after optimizing. The culture conditions obtained by RSM were effective and reliable,the yield of siderophores improved significantly.