Viscosity has great influence on flow patterns generated by like- and unlike-doublet impinging jets. In this research, working fluids adopted herein are viscous water-sucrose solutions with nearly constant surface tension. For like-doublet impingement, as viscosity of working fluid below 2.1 cp (22°C), flow patterns are like those generated by like-doublet water jets. Increasing working fluid's viscosity to 6.6 cp (22°C) appeals complicated periodic drop mode. The higher the viscosity of working fluid, the more complex the flow patterns formed. For unlike-doublet impingement, flow patterns generated by impingement of water and fluid 5 exhibit the same as those generated by like-doublet impinging fluid 3 jets. Besides, at low jet velocities, density ratio has a little effect on atomized SMD. SMD reaches 100μm at high jet velocities regardless of density ratio of impinging pairs.