The soil organic matter content in saline-alkali soil is low, and under conditions of high salinity and high pH, the natural process of soil organic matter accumulation in saline-alkali soil is extremely slow. The application of exogenous organic materials to promote soil organic carbon (SOC) accumulation is essential for improving soil fertility in saline-alkali soil. In this study, a field experiment was conducted to investigate the effects of applying vermicompost and vinegar residue at equivalent carbon rates (5‰, 7.5‰, and 10‰) on soil organic carbon accumulation in saline-alkali paddy soil. The results showed that applying vermicompost and vinegar residue promoted SOC accumulation. Compared with the control treatment, the SOC content increased by 112.8% and 33.9% with the highest application rates (10‰) of vermicompost and vinegar residue, respectively. Furthermore, the SOC content in vermicompost treatment was on average 59.0% higher than that in vinegar residue treatment. Application of both vermicompost and vinegar residue increased the contents of soil dissolved organic carbon (DOC), easily oxidizable organic carbon (EOC), particulate organic carbon (POC), mineral-bound organic carbon (MOC), and the carbon pool management index (CPMI). Under the condition of equal carbon application, the above-mentioned indices in the vermicompost treatment were 13.0%, 33.8%, 177.1%, 32.2%, and 17.5% higher than those in the vinegar residue treatment on average. In addition, the application of vermicompost and vinegar residue was beneficial to the formation of soil water-stable aggregates and the reduction of soil pH and electrical conductivity (EC). Results from correlation analysis and random forest models showed that the increase in organic carbon content of each soil component, the formation of water-stable aggregates, and the alleviation of salinization and alkalization all contributed to the SOC accumulation in saline-alkali paddy soil, especially the increase in the contents of MAOC and POC. In conclusion, the application of vermicompost and vinegar residue promoted the SOC accumulation in saline-alkali paddy soil. Under the condition of equal carbon application, vermicompost application was more conducive to SOC accumulation.