The invention provides an automatic gas sampling process and a device thereof at the site of an accident, wherein the device is installed nearby a chemical production device in advance, and can automatically start to collect gas sample in real time or delayed time and store the gas sample in a sealed container when an accident of leakage, burning or explosion of a chemical device happens. The device comprises: a sensor system for transforming information of surrounding pressure, temperature and sensitive gas concentration into electric signals by a sensor; a judging system for intelligently judging whether the accident of explosion, burning or leakage happens; and a sampling system for starting a gas sample acquisition system immediately or in delayed time when the accident happens.