The arbitrary estimation of the shape of background adversely affects the results of quantitative analysis because of over- or under-estimation of peak area. Especially, the resultant background by the iterative Shirley method that is widely used is strongly dependent on the operator's choice of the starting and ending points on the XPS spectrum. To decrease this undesirable dependency, we focused on the active Shirley method, which automatically adjusts the background intensities at the starting and ending points during the peak fitting process. We installed this method into the COMPRO software and performed the peak fitting of Cu 2p spectrum in Bi-based superconductor and the thickness determination for SiO2 / Si thin film on the GUI of COMPRO. The shape of backgrounds and peak areas were stably obtained by using the active Shirley method with various ending points of background and peak shapes of Voigt functions.