Oxygen is the key material of metabolism of human body and the first need of human life activities. Explosion in coal mine production and natural disasters such as seismic hazards and geological hazards will lead to collapse, burying and accumulation, and then a complex enclosed environment will take shape. If there are signs of life in the enclosed environment, the disaster relief work will be particularly important. In particular, the measurement of oxygen content and it’s concentration change with time in enclosed environment is of very important significance to the operation of the disaster rescue robot. Therefore, an experimental system for quasi-continuous modulation laser absorption spectroscopy measurement is established, whose research object is closed in door oxygen. We measured the closed indoor oxygen concentration’s change during 24 hours based on tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS)The quasi continuous modulation laser absorption spectrum method can accurately measure the closed indoor oxygen change.