Abstract: In experiment and theory,the studies on the third continuum of argon in the word are introduced In experiment,with different pumping ways,the shape of fluorescence and time resolved spectra are measured Up to now the small signal gain of this continuum has been reported In theory,with the calculations of spectrum and kinetics,the origin of the continuum is studied There are two main hypothesis that the continuum can be emitted by the transition of Ar22+ and Ar2+ ionic excimers Because either of the two hypothesis can only interprete a part of experimental results,there are no identical conclusions about the origin of the third continuum.