We used the incoherent broadband cavity enhanced absorption spectrascopy for measurements of NO2. We use the blue-light high power LED as the light source, measuring the absorption of NO2 with the specturm range from 455 nm to 465 nm.The calibration principle is that the rayleigh scattering between nitrogen and helium have a big difference and the high mirrors calibrating reflectivity from 455 nm to 465 nm all higher than 99.99%, the maximum point at 455.2 nm can reach 99.9908%. Under the condition that the effective cavity length is 92 cm and the intergral time is 30s, we measured the sample’s sperctrum which have NO2 absorption and recovered it by a software named DOASIS, and found that the NO2 concertration is equivalent to 21.25±1.7ppb, the uncertainty is approximate 8%.The calibration result y=1.001x+0.271 show that the technology is very reliable to measure NO2。