Since 1997, 13 provinces and regions in China have experienced grass pest disasters. The average annual hazard area comprised more than 3 million mu and the annual economic losses totaled more than 20 billion Yuan. Because grassland encompasses very large areas, grass pest disasters occur suddenly and frequently; thus, they are very difficult to predict and subsequently monitor. In order to provide technical support for grassland plant protection, we need to develop effective early warning systems and effective control measures. Herein, we develop and evaluate GPC (Grass Pest Control information system), a web-based expert system for identification of grass pests, which included more than 50 species of grass pests. It has been developed by China Agricultural University and Institute of Plant Protection, Chinese Academy of Agricultural Sciences. Based on user needs, GPC was developed with ASP.NET, C# and Microsoft SQL server 2008 database. In its development we used 8 databases including a user information database, basic information database, and identification knowledge database. This tool and information database was developed both for grassland plant protection technicians and farmers.