We developed the Regional Methane Assimilation System (RegGCAS-CH4) based on the WRF-CMAQ model and the EnKF algorithm. By assimilating extensive TROPOMI column-averaged dry CH4 mixing ratio (XCH4) retrievals, we conducted high-resolution nested inversions to quantify daily CH4 emissions across China and Shanxi Province in 2022. Nationally, posterior anthropogenic CH4 emissions were 45.1 TgCH4·yr⁻¹, 36.5% lower than the EDGAR estimates, with the largest reductions in the coal and waste sectors. XCH4_2022_China.nc and XCH4_2022_Shanxi.nc contain prior and posterior XCH4 simulations, as well as TROPOMI XCH4 observations over China and Shanxi Province.SURFCH4_2022_China.nc and SURFCH4_2022_Shanxi.nc contain prior and posterior concentration simulations of surface-level CH4 over China and Shanxi Province.RegGCAS_CH4EMIS_2022_China.nc and RegGCAS_CH4EMIS_2022_Shanxi.nc contain the inverted daily anthropogenic CH4 emissions over China and Shanxi Province, respectively.EDGAR_CH4EMIS_2022_China.nc and EDGAR_CH4EMIS_2022_Shanxi.nc contain the monthly anthropogenic CH4 emissions over China and Shanxi Province from EDGAR, respectively.obspack.zip contains CH4 concentration data from five in-situ and five flask monitoring sites.