The embodiment of the invention discloses an extracted polluted gas online monitoring system in a soil remediation process. The online monitoring system comprises a continuous acquisition monitoring system and an automatic data acquisition system. The system can automatically monitor, measure and count extracted gas phase parts (non-methane total hydrocarbons, benzene and benzene series), can ensure timely, effective and continuous monitoring and recording of various data, can provide detailed and reliable data for project supervision, and detailed data for future acceptance check, and can also be used for developing the optimal solution for the next-step remediation. The embodiment of the invention also provides an extracted polluted gas online monitoring method in a soil remediation process.