Abstract: The preparation and purification in the experiment of Fe(OH)3 colloid electrophoresis had been discussed in detail. This experimental determination method was introduced and the result as: iron hydroxide colloid was prepared with iron chloride and urea by the fast hydrolysis. Then, we used the dialysis bag to purify colloid. HCl+KCl mixture solution with the same conductivity of colloid had been chosen. ζ-potential values were obtained accurately and repeatable, this method was simple and also suitable for students.