Resource-based cities experience rapid urban development by resource mining and maintain ecosystem stability by ecological restoration. Assessing negative and positive impacts of typical human activities on ecosystem services of resource-based cities is of great significance for sustainable urban development. Taking Ordos, Inner Mongolia as an example, this study improved the calculation method of ecosystem service value (ESV) based on the land use/cover and normalized difference vegetation index (NDVI) data. Then the spatiotemporal patterns of regional ESV were quantified from 1990 to 2018. We selected the urban expansion and ecological restoration as the typical human activities. The positive and negative impacts of the human activities on the ESV were then evaluated. Results showed that the grassland and unused land covered more than 80% of the total area in Ordos City. The urban land area indicated a general increasing trend mainly by occupying cropland and grassland, with an annual increasing rate of 0.36%, 4.34% and 10.27% during 1990-2000, 2000-2010 and 2010-2018, respectively. The woodland area showed a continually growth during the three periods and the grassland area increased since 2000. Both of the increase were mainly converted from the unused land. The total ESV of Ordos City generally increased from 231.22 billion yuan in 1990 to 242.14 billion yuan in 2018 with an increase rate of 4.72%. Driven by the land use/cover changes, the spatial pattern of ESV change varied in time and space. The hotspots with significant ESV increase moved from northwest of Hangjin and Donsheng District during 1990-2000 to south of Hangjin and Yijinhuoluo during 2000-2010 and southwest of Hangjin during 2010-2018. The cold spot with significant ESV decline were mainly located in the middle of Hangjin during 1990-2000 and 2000-2010, in Dalate-Dongsheng-Yijinhuoluo belt. After the year of 2000, the returning cropland to forests and the restoration of unused land in Ordos City made an ESV increase of 11.35 billion yuan. And meantime, the occupation of ecological land and production land by urban expansion led to a decrease of 9.14 billion yuan in ESV. We conclude that the positive influences of ecological constructions were greater than the negative impacts of urban expansion. The coefficient adjustment of the ESV is beneficial to differentiate the ESV provided by grassland and forest with different coverage. We suggested to pay more attention to the protection and restoration of grasslands with mediate or low coverage in order to improve the regional ecosystem services.