Abstract: A blue light emitting diode (LED) based incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument was set up for high sensitive detection of NO2 molecule. A detection sensitivity of 3.210-9 cm-1 (1, 300 ms integrating time, and 10 times average) was demonstrated on the basis of absorption spectroscopy of NO2, corresponding to a minimum detection concentration of about 187 pmol/mol for NO2. The measurement sensitivity and optimum acquisition time of the IBBCEAS system were evaluated using Allan variance analysis. The detection limit of 44 pmol/mol for NO2 was achieved with an optimum acquisition time of 30 s. The IBBCEAS measured NO2 data in ambient air were compared to the values measured with an online NOx analyzer (Thermo 42i). Result shows a good agreement between the NOx analyzer and the IBBCEAS.