The invention discloses a gas-sampling chamber which is applied in infrared gas analysis instrument (or sensor) field, is capable of reducing the affect of dust and water vapour on measurement accuracy furthermost so as to improve measurement accuracy. The chamber structure comprises a cavity body which is provided with an opening that allows an inner cavity to be communicated with the outside and a window that beam can permeate, and is characterized in that the inner cavity of the sampling chamber is also provided with a device that is capable of blocking the reflection of beams, which can be realized by making the inner cavity wall more rough, making the inner cavity wall with material that absorbs infrared light intensely, painting substance that absorbs infrared light on the inner wall surface or arranging a reflected light blocking ring that can block reflected light from entering the infrared detector in the sampling chamber cavity body. Then the rate of the reflected light reaching the infrared detector is approximate to zero, thereby improving the anti-dust capability and the anti-water vapour interference capability of the infrared gas analysis instrument (or sensor).