Abstract: Relation between Sn whisker growth and the amount of rare earth was studied.The influence factor of Sn whisker growth was initially analyzed, especially in the aspect of aging time and cooling rate.Furthermore, the growth mechanism of Sn whisker growth on the surface of the solder was initially discussed.The experimental results show that with the addition of 0.7% Pr to Sn-Zn-Ga-xPr solder, Sn whisker could spontaneously grow on the surface of the solder only after aging 12 hours.With the increasing of aging time, the length of Sn whisker grew rapidly, which could reach the critical value of failure after aging about 45 days.It was also found that the growth morphologies of Sn whisker with different cooling rates have diversity.Finally, the mechanism for whisker growth in Sn-Zn-Ga-xPr was initially discussed.