The invention provides a plant population microenvironment control device and method. The plant population microenvironment control device includes a box body, a first sensor box, and a dehumidification and cooling device vent. Through sensors in the first sensor box, a morphological structure of the plant population and environmental parameters in the box body are detected. Based on detection results, the light intensity, temperature and humidity in the box body are adjusted by using the functions of an electrochromic material covering the surface of the box body and a dehumidifier or an air-conditioning fan. The plant population microenvironment control device can achieve the precise control of the microenvironment of the plant population to be measured under the premise of ensuring thenatural growth of the crop population to be measured during the non-measurement, including light environment, temperature and humidity, etc., and at the same time, realize the measurement of the morphological structure, assimilation rate, light distribution and the like of the crop population.