This study evaluates the economic value of grassland tourism in Inner Mongolia, China, using mobile phone signaling data to track tourist flows from 333 cities to 103 counties in 2020. A zonal travel cost model, both parametric and non-parametric, was employed. Results indicate the tourism value ranged from 585.9 to 598.4 billion CNY (US $84.9–86.7 billion), about 2.5 times the tourism revenue, constituting 29% of regional GDP. In the absence of COVID-19, the value would have reached 936.5 billion CNY. The study reveals spatial disparities, with grassland quality, infrastructure, and regional development driving tourism value.