The Taiwan Army's soldiers with flatfeet had sports injuries while accepting long-term training. They would have the risk of dangers even though that they did not reach the criterion (the angle of fifth metatarsal-calcaneus>165°). Therefore, We recruited the subjects aged from 18 to 25 males (flat 172.3±4.8cm, 67.0±7.6kg, 56 feet and normal 176.2±6.6cm, 69.6±9.6kg, 30 feet) through calculate parameter of footprints, and examined the foot parameters in order to find out more proper and easier standard of judgment. Then t-test (α=.05) was used to differentiate between the normalfooted and flatfooted (X-ray>165°). This study also constructed a test of criterion-referenced in nine measurement indexes, by logistic regression analysis establishment formula (according to standards AI>0.26, AI>0.30, X-rays > 165). Three findings were obtained. First, there was a best logistic regression analysis establishment formula: that is, Logit p=9.072+(-8.282)× Arch Leight Ratio. It reached 82.9% of the explanation strength. Secand, the probability of predicting the flatfooted reached 82.9%. It showed that the prediction accuracy was high, ROC curve (Receiver Operating Characteristic curve), and rises fast demonstrated the Logistic pattern quality and prediction of the accuracy were high. Therefore, it was suggested that was a good and easy way to measure the footprints by Arch Leight Ratio for the Army and the shoes designers to discriminate flatfooted from the normal. Third, there were significant differences (p<.05) on dorsum of foot (N/F7.76±0.62/7.13±0.78), on the angle (M5-calcaneus) (N/F156.18±5.43/167.22±3.60) by X-ray, Arch Index (N/ F0.28±0.05/ 0.34±0.05), and Arch Length Ratio (N/F1.249±0.384/0.22±0.67) between the normal and the flatfooted. There were no significant differences on Arch Ratio (N/F0.37±0.03/0.36±0.04). It meaned that there were different results in judging flatfeet by the Arch Leight Ratio and X-ray. We suggested that many ways of Arch indexes of feet need to be researched and discussed.