The spectrum of carbon monoxide was obtained around 1.573 μm using a tunable distributed feedback semiconductor laser with a high-finesse cavity at room temperature via off-axis cavity enhanced absorption (CEA) spectroscopic technique. The absorption line of carbon monoxide at 6 357.311 6 cm-1 was chosen for trace detection. Meanwhile, in order to get more accurate measurements, absorption path length of the cavity calibration methods was studied, and a simple and practical calibration method was given. The results show that, the equivalent absorption path length of high-precision optical resonator was ~1 195.73 m. At last, we got the concentration of carbon monoxide in the real atmosphere to be ~388.346 ppm (S/N≈22), and the detection limit of carbon monoxide was 17.65 ppm. By combination of wavelength modulation technology and OA-CEAS technology, a minimum detectable concentration of 0.36 ppm (S/N≈1 064) was achieved eventually.