Differential optical absorption spectroscopy technique (DOAS) has been used to measure trace gases in the atmosphere. This technique uses the gases strongly structured absorption of radiation in the UV and visible spectral range to retrieve their concentration. The measurement on monocyclic aromatic hydrocarbons (MAHC) was carried out using the portable DOAS system developed by Anhui Institute of Optics and Fine Mechanics. The retrieval method for measuring MAHC with the system and the effect of relative retrieval and absolute retrieval methods to remove the interference of O were analyzed. The detect limits of portable DOAS are given. The results demonstrate that the portable DOAS system can be applied to polluted sources of MAHC and polluted gases leak monitoring.