The history，status and developments in the definition of the kilogram mass unit

Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last manmade standard to be used to define a basic SI unit, and its redefinition will influence several other base units. This paper describes the principle of the watt balance and the experimental determination of Planck's constant. These results are of great significance for physics and metrology.