Soil organic carbon (SOC) is the most active component in terrestrial carbon pool. Small variations in global SOC stock could result in significant impacts on the atmospheric CO_2 concentration and contribute to global climate change. In this study,we collected 528 soil samples at 77 sites from different natural ecosystems (desert,grassland,shrubland,and forest) in northern China. We compared the differences of SOC concentrations in different ecosystems and analyzed the influencing factors on SOC concentrations. The results showed that SOC concentration was the highest in forests,with an order: forest > shrubland > grassland > desert. The SOC concentrations were significantly positively correlated with mean annual precipitation,clay content, silt content,NDVI,and plant species richness,but negatively correlated with mean annual temperature,soil pH,and sand content. We found a positive but insignificant correlation between SOC concentrations and plant species alpha diversity. The variations of SOC concentrations were mainly driven by soil,climate,and vegetation factors at regional scale.