We propose a periodic table for quadrilateral tetra atomic molecules. Each molecule consists of four atoms, and the geometric shapes of these molecules are studied by ab initio calculations. It is found that by increasing the valence electron numbers, strong periodicity appears with many molecular properties. The periodic table for the quadrilateral tetra-atomic molecules is considered as an extension of Mendeleev's periodic table. It can also be used for estimating the unknown properties of tetra-atomic molecules.