In recent decades, urban areas in China have been rapidly increasing. This urban area expansion has caused land use changes, which have enormous inuences on regional ecosystems. The potential environmental problems caused by urban expansion have attracted extensive attention from researchers. Net primary productivity (NPP) is the amount of solar energy converted to chemical energy through the process of photosynthesis. NPP loss may affect the composition of the atmosphere, fresh water availability, biodiversity, and the ecological adjusting mechanism of energy supply and distribution. Moreover, NPP is also an important ecosystem productivity indicator. Hence, studying the impact of land use changes, caused by urban expansion, on NPP is crucial to understanding ecosystem structure and function changes. In recent years, Shenyang Metropolitan Area has experienced rapid economic growth and industrial development under the guidance of the central government policy and local government strategy. As a result, urban area expansion of Shenyang Metropolitan Area has also accelerated, resulting in significant land use changes. The 10 years from 2000 to 2010 were representative of the process of Shenyang Metropolitan Area's urban expansion. This study analyzed land use changes with Shenyang Metropolitan Area from 2000 to 2010. Six categories of land use types were interpreted from Landsat TM/ETM remote sensing images: forestland, farmland, urban area, grassland, wetland, and bare land. NPP changes in the study area were estimated through the CASA model. The spatial and temporal dynamics of NPP were studied in regional and land use categorical scales. There is little prior research investigating this change trajectory of NPP under different land-use conversion types. The change of NPP caused by urban expansion of Shenyang Metropolitan Area was analyzed. The results showed: (1) Farmland, forestland, and urban areas were the main land use types within the study area. Rapid urban expansion and loss of farmland were the predominant land use changes. While the area of forestland decreased, grassland, wetland, and bare land area changed only slightly. The demand for land for urban construction was greater in 2005-2010 than the demand in 2000-2005; (2) The NPP of the study area decreased, and changed greatly both in spatial and temporal scales. The NPP decreased more rapidly in 2000-2005 than it did in 2005-2010. The NPP decreased in all of Shenyang Metropolitan Area, except for Fuxin City. The highest values of NPP reduction were in the eastern part of Shenyang Metropolitan Area and the lowest values were located in the northwest region of Shenyang Metropolitan Area; (3) The mean NPP in the six land use types declined. Forestland declined most rapidly and the conversion of farmland to urban area had the largest annual NPP loss. From 2000 to 2005, annual NPP loss from the conversion of farmland to urban area was 21886.68 tons/year. However, from 2005 to 2010, NPP declined to 7003.61 tons/year from the conversion of farmland to urban area. NPP loss was relatively high in the following conversion modes: forestland-farmland, forestland-urban area, and farmland-wetland. However, increases in NPP were observed in the conversions of wetland-grassland, wetland-bare land, and bare land-grassland.