Abstract: The process of photosynthetic production of crop is divided into three steps for analysing their limiting factor and photosynthetic efficiency. On this basis, the parameters are determined and a calculation Scheme is established, meanwhile the temperature correction being made. Taking Luancheng as an example, the potentiaI productivities of wheat, maize, rice and for different cropping system have been investigated. Finally, some measures for increasing the potential productivity and the efficiency of utilization of light and heat are discussed.