Normalization process is a set of operations whereby systematic biases are removed from microarray data. Therefore researcher can attain acceptable results and have more logic comparisons. This process considering the bias constructions and the effects on microarray is recognizable and applicable. Examples of this process are spatial correction, background correction, rescaling, dye effect and within slide normalization. Spot intensity standard deviation is decreased by that normalization processes, and confidence to the microarray data analysis outcomes is increased. This paper describes all of these methods. In addition it contains the examples of a real dual channel cDNA microarray experiment to illustrate normalization process.