Due to the rapid development of economy, a great deal of cultivated land was transformed into residence, roads and industry area. In order to support policy-making for cultivated land protection, it is necessary for land administration to understand the quality and quantity of land change. However, the traditional way to update the land data is outdated and difficult to accurately acquire the spatial location of the changed boundary and map the change. Surveyors' carelessness often affects the accuracy. Based on the analysis of various GPS differential methods, this paper proposes a new method to use mobile differential GPS technology to update the land use data. The method is implemented in Baotou City to update the land use data of 1992. The result shows that it has the advantages of high accuracy, efficiency and easiness to manipulate. The GPS data can be easily transferred to GIS system to establish cadastral management information system and output paper maps.