[Objective] Soil total organic carbon (TOC) and its various components are critical indicators for assessing soil quality, significantly impacting cultivated land productivity and crop yields. This study aimed to investigate the effects of 12 different exogenous organic materials (including tobacco stalk biochar, fruit tree branch biochar, wheat straw, rapeseed straw, chicken manure, cow manure, glucose, cellulose, LB medium, polyacrylamide (PAM), humic acid fertilizer, and chitosan) on the physicochemical properties and soil organic carbon fractions of typical loess (Black Loessial Soil and Loessial Soil). [Methods] Organic materials were mixed with air-dried soil at a mass ratio of 3%, and a 100-day indoor incubation experiment was conducted, with a control group (CK) without organic material addition. This study used density flotation combined with wet sieving to separate and calculate four organic carbon fractions: free particulate organic carbon (FPOC), occluded particulate organic carbon (OPOC), particulate organic carbon (POC), and mineral-associated organic carbon (MOC). Redundancy analysis (RDA) was performed to analyze the relationship between soil physicochemical properties and organic carbon fractions. [Results] (1) Compared with CK, the addition of organic materials effectively reduced the calcium carbonate content of the two typical loess soils, increased soil electrical conductivity, TOC, and total nitrogen (except for cellulose addition), while the mechanical composition remained largely unchanged. (2) Compared with CK, the contents of FPOC, OPOC, POC, and MOC in the soil were all increased, with the largest increments in FPOC observed under the treatments with fruit tree branch biochar, tobacco stalk biochar, and wheat straw addition. In Black Loessial Soil, the corresponding indicators increased by 2158.5%, 1545.3%, and 907.5%, respectively, while in Loessial Soil, the increments were 2971.8%, 1717.9%, and 1730.8%, respectively. (3) There was a highly significant positive correlation between FPOC, OPOC, POC, MOC contents, and TOC (P < 0.01). The C/N ratio and total nitrogen content were the primary factors influencing the organic carbon content of soil components, with explanation rates reaching 76.1% and 76.3% in Black Loessial Soil and Loessial Soil, respectively. [Conclusion] The addition of organic materials increased TOC content and effectively improved soil physicochemical properties. Compared with CK, the contents of FPOC, OPOC, POC, and MOC in the soil were all increased. The C/N ratio and total nitrogen content were the dominant factors influencing the organic carbon content of soil components.