In this study, gaseous element mercury (GEM) and gaseous oxidized mercury (GOM) inthe atmosphere were continuously observed at a minute resolution from 1 April 2019 to 31 December2020 in urban Xi’an, the largest central city in Northwestern China. The concentrations of GEM andGOM drastically fluctuated within the ranges of 0.022–297 ng/m3 and 0.092–381 pg/m3, showingaverage values of 5.78 ± 7.36 ng/m3 and 14.2 ± 20.8 pg/m3, respectively. GEM and GOM showed adecreasing trend of 0.121 ng/m3 and 0.472 pg/m3 per month, respectively, which we believe wasmainly caused by anthropogenic sources, especially by a reduction in coal-fired emissions, ratherthan meteorological factors. The significant positive correlation between GEM and PM2.5, SO2, NO2,and CO, as well as Cr, As, and Pb in PM2.5 also proves that. GEM showed a higher concentrationat nighttime than daytime, while an M-shaped diurnal trend was observed for GOM. The hazardquotient of GEM for both males and females decreased at a rate of 0.003 per month, and children aged2–5 were more sensitive to non-carcinogenic health risks. The changing trends, controlling factors,and human health risks of Hg in the atmosphere are necessary and crucial to study for improvingour understanding of the impacts of Hg in Northwestern China.