The temperature of workpiece irradiated with CO2 laser is measured using a new type of infrared radiation pyrometer with an optical fiber. In the pyrometer, a chalcogenide optical fiber and a two-color detector which consists of InSb and InAs detector are used. The power intensity of the laser beam during the exposure time and the two dimensional picture of the intensity distribution of the laser beam are measured experimentally. The measuring system for the intensity distribution of laser beam consists of MCT cell and an optical fiber. The temperature distribution on the workpiece irradiated with laser is calculated numerically using FEM for unsteady state. The change of physical properties of materials is considered. Comparing the experimental results with the calculated ones, the absorptivity of the work material for CO2 laser is obtained.