In Akhakkyebom(낙학궤범), one of the greatest Korean Sources, a great mistake was found in the lengths of the pitch pipes. Whanjong(황종) from which the other eleven pitches are calculated, is nine inches by decimal system. But the rest are from 9inches by nonary system. To find out how such a contradictory combination could put into so great a book, all the sources available wereexamined. In the process of investigating the numeral change of the lengths of the pitchpipes, it was found that fixation of this contradictory combination was due to the tradiction of Confucianism, which is specialized by its adherence of the old. SongHyon(성현) couldn't understand well enough Tsai Yuan-ting's(몽원정) Account of the science of the pitch pipes in Lu-luhsin-shui(율여신서), Neither could Yi Hye-gu(이혜구) who translated Akhakkwebom(낙학궤범) into Korean. The parts they misunderstood were pointed out and explained as it should be in this thesis. Several other accounts of the science of the pitch pipes like Chu Tsai-yu's and Jing Farng's are also explained. The Pitch-pipes which were said to have been made by Pak Yon(박연) were found out to be of Chu Tsai-yu's. Those which Yi Sang dok(이상덕) wrote were one of Pak Yon's achievements turned out to be of Tsai Yuen-ting's(몽원정), And othe interesting mistakes were pointed out in thesis thesis. Most of these mistakes were made, I think, because of the lack of the study on the historical background. That's why I tried to examine all the sources available on pitch-pipes. In the lengths of the pitch-pipes preserved in Shih-chi(사기) by Ssu-ma Ch'ien(사마천), several letters were found to have been misprinted. Some 칠's should be “십” and the letter “일” in Hyopchong(황종) should be “칠”. I couldn't deal with all the lengths of the pitch-pipes in this thesis. Especially the real length of the old measure of Whangjong(황종) made by PakYon(박연) is remained still unknown. I believe a lot more study should be poured on this field to know our traditional music as it was.