Abstract: Abstract: There are two of the main practical monitoring approaches in agriculture including remote-sensing monitoring and on-farm monitoring. Remote-sensing monitoring uses remote-sensing technologies and devices such as satellites and aerial vehicles to extract the key parameters of agricultural information. The remote-sensing technology is effective on regional-scale monitoring, but difficult to collect real-time information in farmlands. On-farm monitoring uses a variety of sensors deployed in farmlands as well as corresponding data processing and transmission equipment to dynamically acquire on-farm information. The Internet of Things (IoT) technology based on the sensor nodes has been widely used in the field of agricultural environment monitoring in recent years. However, when a regional-scale monitoring is carried out by using the IoT technology, there are some problems in the distribution of monitoring sites and the space representation of monitoring data. Aiming at the problems, an approach to evaluation of agricultural environment from on-farm sites to regional scales and the corresponding solution are proposed in this paper. Most of the factors of agricultural environment remain minor variation and appear to be uniform in the same ecological type region, except for extreme weather events or geographical conditions. Therefore, the agricultural environmental information acquired by an on-farm monitoring site could be regarded as the representation of the entire farm where the site located, and the agricultural environmental information of a representative farm could be also considered as the reflection of an entire ecological type region with similar geographical and environmental conditions. An IoT-based monitoring system has been put into application in the past five years which includes a total of 110 on-farm monitoring sites in representative regions of wheat belts across 14 provinces of China and a central monitoring platform. Based on the established central monitoring platform, a regional-scale monitoring system for agricultural environment is designed by integrating with the spatial analysis technology of WebGIS. In the system, three types of WebGIS-based functions were implemented, including site data positioning, regional-scale evaluation, and thematic mapping. Through an interactive online map, positioning, real-time display and query of on-farm sites information and collected data are realized in the site data positioning. The regional-scale evaluation is used for analysis of the collected agricultural environmental information, and decision-making on crop growth conditions and meteorological disasters from on-farm sites to regional scales, while the thematic mapping is used for automatic generation, dynamic display and query of regional-scale monitoring thematic maps of crop growth conditions and meteorological disasters based on the evaluation. The fusion analysis of "on-farm" IoT data and "spatial" WebGIS data is provided in accordance with the characteristics of monitored objects. The system has been put into application in monitoring of wheat growth conditions and meteorological disasters in Henan Province. And the case is demonstrated in dynamic regional-scale monitoring of wheat dry-hot wind occurred on May 11, 2013 in Henan Province. The result indicates that the system is effective when monitoring agricultural environment from on-farm sites to regional scales with dynamical update and the applicability on diagnosis in crop growth conditions and meteorological disasters is improved.