Optical waveguides have a promising application as absorption cells in concentration measurement for gases. Mechanism and properties of the time response for the waveguide absorption cell were theoretically analyzed based on the diffusion and hydrodynamic theories. Two measuring systems corresponding to the diffusion and hydrodynamic applications were established by using Fourier transform infrared spectroscopy (FTIR) equipment, Ultraviolet and visible (UV-VIS) spectroscopy and specially fabricated low-loss hollow fiber as the absorption cell. A modified calculation model was proposed based on the measured data of dynamics methane and toluene gas flow at low concentration level. Experimental results show that response time can be dramatically shortened by optimizing the structure of the waveguide cell while maintaining a high sensitivity in gas sensing. And the characterization results provide useful guidance for the design and application for gas sensor using hollow waveguides as absorption cells.