A new method (the CMB-Iteration method) was developed and applied to estimate primary organic carbon (POC) and secondary organic carbon (SOC) concentrations in ambient particulate matter. In addition to the concentrations, this model also calculates the source contributions to POC and SOC. For each source category, the estimated source contribution is continuously calculated until the iteration minimum is achieved, i.e., the ratio of the estimated source contribution at the final step iteration to previous step iteration is less than 0.01. The application of this method is used to analyze a reported database. The result of the CMB-Iteration method is consistent with in the reported result in the literature. Additionally, synthetic datasets were analyzed using the CMB-Iteration method, and acceptable results were obtained. Finally, this method is used for a dataset collected from Taiyuan, China across different seasons (winter and summer). The calculated concentrations of SOC are 14.3 and 10.7 mu g/m(3) in winter and summer, respectively, suggesting that there are high secondary OC particles in this highly polluted city (Taiyuan).