The dimension of nano-particles is close to the dimension of colloid particles. The dispersion system of nano-particles is colloid. The sedimentation rate of nano-particles dispersed in water is calculated, and it is shown that the sedimentation rate is very slow and the nano colloids have high stability on dynamics. Those conclusions are approved by tests. The influence of electric characters of the colloid and macromolecule was introduced. The results of the study maybe out of the image of most people and are useful to change their attitude of the kinetics stability of real nano particles colloid.