The concentration field in a horizontal double-nozzle liquid-liquid impinging stream mixer was analyzed qualitatively and quantitatively with planar laser induced fluorescence technique. The time average mixing efficiency was evaluated withg intensity of segregation (IOS), its varation along the radial direction of jet flow was examined under different operation conditions, and compared with that in the three-nozzle impinging mixer. The results show that the distance between nozzles (L), diameter of nozzle (D) and lquid flow rate (Q) have important effects on the mixing efficiency. In the horizontal double-nozzle impinging mixer, the declining speed of IOS increases with the increase of L under the same D and Q, the optimal L is 3D. The declining speed of IOS increases with the increase of D, reaching 0.05, the necessary distance continuosly decreases, the optimal D is 12 mm. Under the same D and L, the declining speed of IOS increases first and then decreases with the increase of Q, the optimal Q is 500′10-3 m3/h. The three-nozzle impinging stream and horizontal double-nozzle one have the similar changing trend.