It is very difficult to joint two television-images correctlly and a light or a dark line appears at the joint of the compositive image. To eliminate the line, we suggest a method that apply the characteristics of visual contrast threshold value on the brightness of the cathode ray tube (CRT). As the input signal is obtained theoretically from the relation between the spread function and the brightness of CRT, the image-composition is accom-plished by the composition of the signal waveforms, which are superposed each other by the cross fade. The jointing range and the fading form are deter-mined from the contrast threshold value so as not to perceive the line. The paper describes that the composition of digital images is possible in the range of a few picture elements.