The determination of physiological parameters of plant leaves is of great importance to the study of plant growth and development. In order to realize the low-cost and high-efficiency monitoring of physiological parameters such as plant photosynthesis, a monitor with automatic opening and closing and handheld leaf chamber is designed in this paper, which can collect and manage experimental data by connecting nodes and computing nodes. The data collection such as CO₂ concentration, air temperature and humidity, atmospheric pressure and real-time calculation of photosynthetic physiological parameters are completed through the access node. The data storage and networked transmission of the human-computer interaction interface and remote monitoring system are realized through computing nodes. The results show that there is no significant difference between this instrument and similar monitoring systems abroad, and it can meet the requirements of automatic monitoring of plant photosynthesis. In addition, the monitor has fast response to automatic monitoring of plant physiological parameters, stable and reliable measurement results, and low cost. It plays an important assistant role in monitoring crop growth and development, guiding crop fertilization, and preventing plant diseases and insect pests.