A method presented by authors calibrates monitor in terms of CIE XYZ coordinates. In the paper following steps of the calibration process are considered: a mapping of luminance of a phosphor to a voltage, which is applied to corresponding gun of a color monitor, guns balancing, and a calibration of a color. This method does not use additional measurers. All data needed for displaying colors of given CIE XYZ coordinates are found in convenient for a use form. Also the method allows to estimate spatial non-linearities of CRT, giving confidence that the monitor suits for a qualitative displaying.