A definition of biological essential elements was proposed. Their origin and function in human body were discussed. An excellent strain Sl of Tetrahymena, a kind of ciliates, has been used in this study to observe both stimulation or nutritious and toxic inhibition effects of elements located in s block, p block, d block, and f block in the periodic table, some regularity between the biological effects of these elements and their positions in the periodic table has been obtained. It is shown that a “spectrum of biological element equilibrium”, which exists in organism, can be exhibited in the periodic table designed in the three-dimensional space, if the abundance of biological elements or/and their bioavailability is used as the third z axis, a vertical line to the plane of the periodic table, and then the biological element spectrum shows that the exchanges of matter and energy between organism and surface environment of the earth have reached the dynamic equilibrium state. It seems that not only physical and chemical properties of different elements and compounds, but also their biological properties to a certain extent can be shown in the developed periodic table.
