This paper is a report 011 the observations of saturated optical absorption in chalcogenide glass bulks or films of the As -S-Soz-Tex^ quartenary system under Nd:glass laser irradiation. When sample is placed outside the laser cavity, the nonlinear effect of the light transmission varying with the laser power is observed, and the light transmission of the sample increases by about 30%. When sample is placed inside the laser cavity, the modulated effect is observed. It is considered that the saturated optical absorption in the chalcogenide glasses of As-S -Sef-Te1x system is caused by self-induced dynamic Burslein-Moss shift of the fundamental absorption edge.