Abstract: The process of oxygen-iodine mixing is one of the most important steps in chemical oxygen-iodine laser (COIL). The quality of oxygen-iodine mixing is directly related to the COILs operating efficiency and beam quality. Employing chemical fluorescence method (CFM)，the effects of trip tabs on the process of supersonic mixing of parallel oxygen-iodine flows in COIL was studied. The experimental results indicated that the mixing process with 1# trip tabs was improved obviously. Comparing with the mixing without trips, when using 1# trip tabs, the streamwise distance required by the fluorescence to reach the centerline of the primary flow was shortened largely and the area ratio of fluorescence in the region of iodine dissociation region was enlarged by 4.2 times. When using 2# trip tabs, the streamuise distance decreased further by 40%-60%, and the area ratio value increased by 20%-40% again. Using 2# trip tabs, the mixing processes with and without the primary buffer gas were compared, and the results showed that the latter was better.