Pigment ink was formulated with nano-coated pigment dispersion, prepared via mini-emulsion polymerization. To study the effect of nano-coated pigment, surfactant and humectant on ink-jet printability, the trajectory of droplets with different pigment ink composition was monitored. The effect of ink formulation on the accuracy of printing process of the pigment ink was discussed by study on line width and edge contour of printed patterns. Experimental results indicated that the additives and properties of the pigment ink had a great influence on droplet formation and precise positioning of the printed patterns. The optimal composition for the pigment ink as following: nano-coated pigment dispersion was 20% w/w, surfactant (S-465) was 1.5% w/w, humectant (diethylene glycol) was 30% w/w and defoamer (FB-50) was 0.1% w/w. The prepared pigment ink exhibited excellent freeze–thaw, thermal and centrifugal stability. In addition, the optimal formula was beneficial to form a stable droplet and obtain high precision patterns.