To investigate the atomization characteristics of power law fluid, an impingement jet system is developed in this study. High-speed photography and 3-D phase Doppler methods are used to obtain the breakup regimes, 3-D velocities and size distribution of the droplets. The effects of pre-impinging parameters (injection pressure and pre-impingement length), geometry parameters (orifice diameter and impingement angle) and physical parameters (fluid viscosity) on the atomization characteristics are studied. The spray patterns could be qualitatively categorized into six types: open rim without shedding droplet, closed rim, open rim with shedding droplets, rimless sheet, bow shaped ligament and fully developed. With the increment of injection pressure, the droplet velocity of each direction increases, the droplet Sauter mean diameter (SMD) decreases, the non-dimensional mean droplet size (SMD/D) converges to 0.14, and X-o/SMD becomes about 1.3-1.5 (D is the orifice diameter, and X-0 is the Rosin-Rammler diameter). The axial velocity (W) increases as the impingement angle decreases. Smaller droplets are produced by larger impingement angles, smaller pre-impingement lengths and lower liquid viscosities. The particle size distribution fits in the Rosin-Rammler function. (C) 2015 Elsevier B.V. All rights reserved.