The invention discloses a device for measuring the concentration of pre-selected gas in an object gas sample, which comprises a heriot multiple-pass cell (10) provided with a central shaft (74) and shells (80A, 80B), wherein the shells are arranged around the shaft distantly to provide a sample chamber (84) of tubular form; a gas sample can be pumped through the holes (154, 156) at two ends of the shaft to penetrate through the sample chamber; a first reflector (44) and a second reflector (46) are supported at two ends of the shaft; a light source (as laser or LED) is provided for transmitting light beam; the light beam passes the inlet (30) of the first reflector to enter into the sample chamber; the wavelength of the light beam is a strong adsorption wavelength of the pre-selected gas; the light beam is reflected between the reflectors for multiple times, before passing an outlet (48) of the second reflector to get out the multiple-pass cell and impacting the detector (52).