In solder paste printing, one of the most important parameters is the viscosity of solder paste and solder powder load, and the physical characteristics of solder particles also affect the resulting viscosity. Therefore, the viscosity of solder paste with three kinds of solder particles (original, deformed and coated Sn-Zn-Bi alloy particles has been investigated by capillary rheometry. It is possible to predict reliable viscosity values for solder paste with deformed solder particles using the relation equation of viscosity and strain.