Abstract: The separate optical probes have been widely used in scramjet laser absorption spectroscopy measured system. High resolution flow field cannot be obtained because of the limitation of the probe size. A high-resolution optical measuring ring based on free-curved lens and cylindrical lens was designed for combustion flow field. The beam distribution was determined by numerical simulation. The measuring ring adopted double-layer structure, the transmitters were located at the most edge of each edge. The fan-beam was formed by collimating lens and free-form lens. And then after passing the measuring flow field, the laser beam was defected by the wedge lens and focused by the focusing lens. The measuring ring receiving unit minimum interval was 5 mm, achieved dense array of 88 beams in 5 cm×7 cm space. The beam distribution of the optical system was discussed. The structural design scheme suitable for engine measurement was given. The measurement result shows that the light efficiency is greater than 50%, the total transmission efficiency is greater than 55%. The high-resolution optical measuring ring can be directly connected with the engine body to avoid the interference of environmental factors. The two-dimensional distribution of temperature and concentration in the isolation and outlet of the combustion can be measured.