Quantum dot Cellular Automata (QCA) is an emerging trend in the field of nanotechnology for digital circuits . It has the potential for attractive features such as faster speed, smaller size and low power consumption than transistor based technology. By taking the advantages of QCA we are able to design interesting computational architectures.Quantum dot is basic element of a QCA cell. It made by creating an island of conductive material surrounded by insulating material.QCA cell is arranged as a square pattern with Four quantum-dots.QCA Cells with dots of 2-nm can be used above room temperature.The operating temperature of QCA Cell is highly dependent on the over all size of the Quantum-Dots.