Sampling system and method for automatically sampling urban sewage

The invention discloses a sampling system for automatically sampling urban sewage. The sampling system consists of a sampling subsystem, a metering and sampling subsystem, a refrigeration subsystem and a control subsystem, the sampling subsystem is used for collecting a proper amount of sewage samples while being subjected to constant-temperature heat tracing and conveying the sewage samples to the metering and sampling subsystem, and redundant sewage samples are discharged from an overflow part of the sampling subsystem; the metering and sampling subsystem is connected with the sampling subsystem and is used for metering the sewage sample collected and conveyed by the sampling subsystem and conveying the metered sewage sample into the refrigeration subsystem; the refrigeration subsystem is connected with the metering and sample injection subsystem and is used for refrigerating and storing the metered sewage sample; the control subsystem is used for controlling a sampling process, a metering and sampling proc