The invention discloses a device for detecting the content of heavy metal Cr element in soil by laser-induced breakdown spectroscopy, which comprises an electromagnetic valve A, an air inlet tube, a temperature and air pressure sensor, a soil sample carrier, a feed inlet, an air outlet tube, an electromagnetic valve B, a fused quartz lens A, an optical fiber probe, an optical fiber, an optical fiber connector, a closed laser induction chamber, a spectrometer, a fused quartz lens B, a laser head, an ICCD (Intensified Charge Coupled Device) detector, an external connection cable, a femtosecond laser, a bottom shell, a cover plate and a miniature air conditioner. The laser head, the fused quartz lens B and the soil carrier on the femtosecond laser are located on the shame horizontal straight line, the centers of the soil carrier, the fused quartz lens A and the optical fiber probe are located on the same longitudinal straight line, both ends of the optical fibers are connected with the optical fiber probe and the optical fiber connector, and the ICCD detector, the left side of which is connected with the external connection cable, is mounted on the left side of the spectrometer.