A single photon ionization time-of-flight mass spectrometry(SPI-TOFMS) was applied to the online monitoring of the volatile organic compounds (VOCs) emitted from a plastic company in Pearl River Delta. The source profiles of workshops and sewage treatment station were attained successfully. Over-standard concentration of VOCs has not been found during the monitoring. In addition, the contribution of every pollution source to the internal roads was also evaluated by comparing the source profiles of workshops. This online VOCs mass spectrometry has wide markets in aspects of online VOCs monitoring, emergency detecting, pollution mode recognition and underlying discharge monitoring.