In order to conserve agricultural land and make the best use of environmental resources, scientists have developed hydroponic systems for growing crops and vegetables. At the same time, it has been found that microalgae and crops can interact on the basis of hydroponic systems. However, research on the nutrient utilization aspect of it is still very limited. In this paper, we investigate the nutrient utilization of crops and algae in a co-culture system, thereby contributing to the improvement of crop yields. Nutrient utilization in co-culture systems includes nutrient competition between crops and microalgae, the effect of CO2 produced by crop roots on microalgae, the promotion of nutrient uptake by microalgae in crops and the stimulation of root growth, and the change in system pH induced by nutrient uptake in crops and microalgae. By analyzing these aspects, it plays a key role for both algae and crops to achieve higher yields and good growth conditions in the co-culture system.