In this study, a highly sensitive ozone detection system based on high precision cavity technology was developed. A deep ultraviolet light-emitting diode (DUV-LED) with a center wavelength of 266 nm was used as light source, and an optical cavity with a length of 30 cm was constructed with two high reflectance mirrors with a reflectivity of 99.7%, which achieved an effective absorbing optical path of 84.7 m. Firstly, the stability of the DUV-LED light source and the interference of other gases at the center wavelength were investigated, and the effective cavity length and the cavity extinction value of the system were calibrated. Then, the performance of the system was evaluated using Allan variance, and it showed that the integrated system had a detection limit of 129×10^-12 (1σ) for O₃ at a time resolution of 1 s, with a total system uncertainty of 6.2%. Finally, to verify the environmental adaptability and stability of the system, the system was employed in a continuous 3 d comprehensive field observation at Hefei Science Island (China), and compared with the commercial instrument Thermo-49i. The observation results show that the O₃ concentrations measured by the two systems have good consistency, with a correlation coefficient of 0.98, a slope of 1.01, and an intercept of 0.75. The consistency verifies the accuracy and reliability of the system in measuring O₃, proving that the system can be applied to accurate measurement of O₃ with high sensitivity and high time resolution in real environments.