Chromosome classification is the essential task of karyotyping analysis which is videly used for detecting genetic anomalities. Chromosomes' band profiles based feature vectors are used frequently in the classification of them. Extracting of band profiles specially in the bent parts of chromosome may be lossy. In this study, an special sub-pixel resolution based method for lossless exctraction of chromosomes' band profile is proposed. This method models the skeleton of chromosomes as piece-wise linear equations using normal lines to the chromosome boundary. Based on the obtained model, extracting of band profiles is done by forming the skeleton normal lines in the sub-pixel resolution. For evaluation the accuracy of band profile extraction, a measure defined as "Percent of Band Profile Loss" demonstrates the proposed method as an alternative method which results to lossless chromosome band profile extraction.