A high-spatial-resolution UV imaging system is applied for the experimental study of opposed impinging diffusion flames for the first time, with special emphasis on the characteristics of impinging reaction regions with detailed spatial profiles of OH* emission intensity. Two horizontal opposed concentric nozzles supplying both fuel and oxidizer are used. The effects of velocity and O/C equivalence ratio ([O/C](e)) on the generation of impinging reaction region are discussed. Velocity has less effect on the reactions of impinging region compared with [O/C](e) and has no influence on the production of reaction core area in impinging region. [O/C](e) has a remarkable influence on the generation of reaction core area in impinging region due to the change of reaction region in single-jet diffusion flames. The heights of impinging upward and downward streams (H), namely, the distance from the edge of streams to the opposing center, rise with the increase of [O/C](e). The buoyancy and momentum are the two main factors on heights, and the effect of buoyancy reduces with the increase of [O/C](e). When [O/C](e) is more than 1.10, both the two heights do not vary with [O/C](e), because momentum has more influence on the flame characteristics than buoyancy.