To better understand the spatial heterogeneity of soil inorganic carbon (SIC) in loess parent material farmlands and its complex relationship with soil organic carbon (SOC), field data from farmland sites containing both SIC and SOC from 0 to 100 cm depth across the Loess Plateau and North China Plain were collected. After reorganizing and standardizing, the representative SIC and SOC soil profile datasets were obtained and utilized to analyze the spatial distribution characteristics of SIC and SOC, their interrelationship, and influencing factors in the loess farmlands. The results showed that similar mean SOC stock in the 0-100 cm soil layer across the two regions (6.6 kg/m² in the North China Plain and 6.7 kg/m² in the Loess Plateau). However, there were significant differences in SIC stock, in the 0-40 cm soil layer, SIC stock in the North China Plain (5.9 kg/m²) was significantly lower than in the Loess Plateau (8.9 kg/m²); conversely, in the 40-100 cm soil layer, SIC stock in the North China Plain (10.7 kg/m²) was significantly higher than in the Loess Plateau (8.8 kg/m²). Sites with lower surface SIC levels in the North China Plain were mainly distributed in the Hebei Plain, with longer farming history, which might experience SIC dissolution in association with fertilization. Sites with higher surface SIC levels in the Loess Plateau were mostly found in low fertility soils located in western regions experiencing higher erosion with high-SIC subsoil exposed. A significant positive correlation (P<0.01) was found between SIC and SOC in the 0-100 cm soil layer of the North China Plain, while a negative correlation was observed in the Loess Plateau 0-100 cm soil layer. In summary, the SIC stock and its relationship with SOC in the North China Plain are mainly influenced by agricultural management practices such as fertilization and irrigation. In contrast, in the Loess Plateau, it is related to the spatial redistribution of soil carbon due to varying degrees of soil erosion.