Agricultural lands are one of the foundations of the country's food security. Recently, the problems of management and efficient use of the agricultural lands have become widespread in society, science, and the political sphere. A characteristic feature of the current state of the agricultural lands is the transformational processes taking place on them. This article discusses the approach to studying, monitoring and controlling the transformation of the agricultural lands on the example of the Leningrad region and also suggests the principle of visualization of transformation processes occurring on the agricultural lands. The purpose of this work is a creation of a geographic information system (GIS) for monitoring the transformation processes by analyzing statistical and cadastral data and providing the local administration with proposals for the effective use and management of the agricultural lands. This GIS is one of the tools for implementing the effective land policy of the region. The study is based on the processing and systematization of data, received as a result of monitoring the agricultural lands in 2013-2017, using a semantic (land cadastral) database, a graphic (cartographic) database, taking into account the efficiency coefficients of the agricultural lands use. The result of the work, which has been done, is the creation of a 1:10,000 scale map with the actual boundaries of the agricultural lands, agricultural enterprises and horticultures plotted on it, attached to the coordinate system of the district. This map-scheme visually allows us to identify the features of the transformation processes on the agricultural lands occurring in the territory of a particular area and, thus, to develop proposals for the implementation of the effective land policy.