To improve the wastewater treatment efficiency and enhance the resource recovery efficiency,this paper studied the effects of trace elements,Fe,Mn,Cu,Zn,Co,Mg,on photosynthetic bacteria(PSB) growth in wastewater.Two most prominent factors that influence the biomass of PSB were identified through single element design.Optimal concentrations of these trace elements were found through the Box-Behnken design and the response surface analysis.The results showed that the best situation was as follows: 0.66 mmol·L-1 Fe2+and 0.16 mmol·L-1 Mg2+,the maximum biomass of PSB reached 1 483.5 mg/L,the maximum COD removal ratio was 89.1%,and the additional cost was RMB 0.033 Yuan/t.The confirmatory tests showed that the combination of Fe and Mg achieved a PSB biomass of 1 380 mg·L-1after 72 h,which was 57% higher than the control.Fe and Mg could promote PSB growth in wastewater and enhance the resource recovery efficiency.