Abstract The improved preparation method of Fe(OH)3 colloid was reported with the valuable advantages of low toxicity, non-pollution, etc. In this method, the biodegradable chitosan colloid particles whose ZETA potential and particle size distribution could be objectively estimated by Malvin particle analyzer were used instead of Fe(OH)3 colloid particles. Teaching practice verified the feasibility and advantages of this experiment, which are suitable for students major in pharmaceutical and related specialties.