The invention provides a device for measuring heavy metal elements in gas on the basis of LIBS (laser induced breakdown spectroscopy). The device mainly comprises a laser ablation system, a sample room system and an LIBS measuring system. A sample room adopts a piston type system with the easily controlled air pressure and temperature, that is, heavy metal elements in normal-temperature and normal-pressure gas are detected by an LIBS device, and heavy metal elements in the gas in the high-temperature and high-pressure industrial environment are measured; the device has the characteristics of rapidness, simplicity, convenience and the like and can overcome the defect that high-temperature and high-pressure real-time measurement cannot be realized.