Over the past three decades, the wetlands of the Sanjiang Plain in Northeast China were extensively reclaimed for farmland and suffered from significant disturbance and degradation. We extracted accurate and consistent land use change information for a typical state farm, called Bawujiu Farm, from classified satellite images from the Landsat MSS in 1979, and from the Landsat TM in 1992, 1999, and 2009. The landscape pattern changes of wetland and farmland were then calculated and analyzed spatiotemporally at class level for each year. The results indicate that the rapid agricultural development process has brought about serious wetlands degradation and fragmentation and excessive cropland growth. The spatial feature of farmland expansion is characterized by the radial expansion centered on the newly-built settlements, linear expansion along the roads, canals and rivers, and planar expansion in the irrigation districts. A comprehensive and effective land use planning and management strategy is essential to decrease the unprecedented speed of agricultural development.