In order to cut off the false positive and negative diagnoses occurring in the clinic diagnosis of early lung cancer by laser induced fluorescence,we have developed a system of two image subtraction processing by computer technique.Due to the fluorescence image obtained through the image intensified is monochrome,therefore the color informations of lung cancer fluorescence image were eliminated.In this paper,a processing method of pseudocolor display of image have been presented.We combined this method with computer program to modify the lookup table of the CA6300 imaging cards.,and then,consequently,the pseudocolor display of lung cancer fluorescence monochrome image has been accomplished,which highly enhanced the discrimination of lung cancer image in color.