The Ministry of Environmental Protection and the Chinese Academy of Sciences jointly investigated and evaluated nationwide ecological environmental changes in China from 2000 to 2010. The goal of this project was to acquire information on the change trend of the ecological environment and existing problems on a national scale, summarizing China's performance and experience in protecting the ecological environment. This ecological project handles a great quantity of data, including photographs taken during field work, positional data relating to field work, and original measurements made using many types of professional equipment. To meet the requirements of collecting and inputting these data on the ecological environment rapidly, effectively and in real time, we designed and constructed a nationwide field-data acquisition system for the ecological environment. This field-data acquisition system takes full advantage of modern information technologies, including mobile geographic information system (GIS) technology, mobile intelligent terminals, and 3G networks. Additionally, the system uses a mobile data collection scheme based on ArcGIS for Mobile. There are three components in terms of system function, namely mobile terminals, a system management website and a server. Five processes are included in the workflow of mobile data collection, namely the issuing of tasks, task analysis, data collecting, data uploading, and task reviewing. To complete all these tasks, seven function modules have been developed, namely the production and management of tasks, data browsing, data collection, data synchronization, data checking and review, user management, and a database. The key technologies of the field-data acquisition system for the ecological environment include a mechanism for running the system, data access method, and mobile database technology. These three key technologies are described as follows. The system uses the application (APP) mechanism for running applications because it can take advantage of terminal hardware resources fully and support more comprehensive and abundant functions of the GIS. The system uses mixed mobile data collection modes; online and offline modes are used in line with the network condition. SQLite is used by the mobile database of the system; in addition, the system uses many types of mechanism such as an automatic backup, manual staging, and multiple checking. The system is developed using C# and Java, the database environment of which is an SQL Server 2008 database developed using Microsoft Visual Studio 2008. All designed system functions are realized, including positioning, data collection and data inputting, data verification, data checking, data uploading, and data exporting. The system is applied in the validation of land-cover types in field work and the measuring of ecological system parameters. The application results show that the system realizes the digital collection, intelligent examination, real-time transmission and effective management of field-survey data, simplifies filling programs, standardizes filling content, and improves work efficiency. The system will thus provide effective support for performing similar work in the future.