Abstract: In order to understand the changes in the temperature field and velocity field of the large-scale multi-span solar greenhouse in southern China under the conditions of curtain-fan ventilation, and to explore the ventilation and cooling performance in the greenhouse under this ventilation method, taking the large-scale multi-span solar greenhouse in the Demonstration Base of Guangzhou Agricultural Technology Extension Station as the research object, the steady-state and transient calculations were carried out. The multi-span solar greenhouse established a three-dimensional steady-state and transient calculation model for the research object. The calculation results of the steady-state model were compared with the data obtained from the monitoring points in the greenhouse to verify the reliability of the calculation model. The transient calculation of the wet curtain-fan ventilation conditions was carried out, and the intuitive temperature, speed distribution and change rules in the greenhouse were obtained. The results show that after the wet curtain-fan system is started, the wind speed on the side of the wet curtain can reach 1.6 m/s in the ventilation process, it gradually develops into a high-speed airflow field from the entrance of the wet curtain to the outlet of the ventilator, and the airflow speed is finally stable at 0.8 m/s. The temperature field in the greenhouse shows the characteristics of gradient cooling from the side of the wet curtain to the side of the fan, and it is accompanied by a slight global cooling of the greenhouse. After doubling the flow rate, the turbulence during the development of the velocity field increases, and the cooling speed increases significantly. The results will provide a refe-rence for the normal operation of the multi-span solar greenhouse in South China and the precise control of the microclimate environment in the greenhouse.