A high-performance oxygen detection system enables real-time online monitoring of critical parameters such as oxygen concentration and flow velocity inside the engine， thereby ensuring optimal operational performance. In flow field testing for engines such as scramjets and aircraft engines， the complex environment—characterized by high temperatures， high pressures， high velocities， and limited measurement space—poses significant challenges to high-performance flow field diagnostics. To address these challenges， an oxygen concentration measurement device based on cavity-enhanced absorption spectroscopy （CEAS） was developed. The system incorporates an embedded optical probe structure and is equipped with multi-directional alignment stages at both the transmitter and receiver ends， enabling straightforward optical path adjustment and alignment for practical engineering applications. Experimental results indicate that， under static conditions， the system measured an oxygen concentration of 20.846 ± 0.97%， showing good agreement with the reference value. In shock tube experiments， although vibrations and airflow disturbances during operation affected measurement accuracy， the system successfully captured three distinct states： before the arrival of the incident shock wave， after the incident shock wave passed but before the reflected shock wave arrived， and after the reflected shock wave passed. The measured trends in oxygen concentration align well with theoretical predictions.