This article is based on the study on the utility theory of Unpil (運筆, a brush use based writing method) introduced on the Chapter 21 「Yùnbǐ (綴法)」 of 『Guǎngyìzhōushuāngjí (廣藝舟雙楫)』 that Kāng Yǒuwéi (1858~ 1927) wrote logically about the calligraphic methods in the era of Qing dynasty. Calligraphy is an art that expresses letters through Pilbeop (筆法, writing rules) based on Unpil, which is the way how to use the brush when you express the dots and lines of the letters. In such utility theory of Unpil, however, he did not simply comment how to apply the ink to the brush and how to deal with the brush. In such theory, he theoretically systemized how the calligraphers could reveal their spirits and dignities pursuing the changes that would not subtly cut off in the letters. When you discuss calligraphy, therefore, you must look into Unpil that deals with the brush use. The rule of Unpil, one of the theories of Pilbeop, is based on various kinds of theories depending on the correlation among zhǐ (指, finger), wàn (腕, hand) and bì (臂, wrist), which, however, show a variety of utilities based on such various kinds of theories. Their ultimate purpose lies, therefore in the expression of the letters correctly and beautifully. The theory of Pilbeop systematically theorizes the ways of showing the spirits and dignities of the calligraphers who must pursue endless changes in the letters. This theory should be, therefore, based on the rule of Unpil. The dynamics and Euitae (意態, the attitude of mind) that the letters show are not only depending on the instruments but it is only brushes that can reveal the changes and dynamics of the dots and lines the best. That is why the use of brushes is crucial in calligraphy. You must, therefore, look into the utilities of the rule of Unpil when you look for the aesthetics of calligraphy. Thus, Kāng Yǒuwéi emphasized that Bangpil (方筆, making squares by brush) must not only draw the shapes but also reveal the aesthetic sense of Ungjeongchimchak (凝整沈着) that looks righteous, well-organized, not too much excited and well-positioned. In order to reveal the aesthetic sense of Wonpil (圓筆, making circles by brush), he emphasized that the Unpil must realize ultimately Sosanchoil (蕭散超逸) that looks natural and bold in terms of form and disinterested and not flesh in terms of Pileui (筆意, intension of brushing). Eventually, he claimed the theory of full-scale utility in the relation between Bangpil and Wonpil. “Bangpil is good for Haeseo calligraphic style while Wonpil for Haengseo and Choseo calligraphic styles”, he said, “Haeseo calligraphic style would lose its freewheeling mood without Wonpil while Haengseo and Choseo calligraphic styles lose their powerful changes without Bangpil. Therefore, Bangpil and Wonpil must be used further in combination”. That is, he emphasized that Bangpil and Wonpil must be used in combination. Pilbeop is superficially a form of expressing beauty, which, however, has the theoretical enlightenment. It is the realization of beauty to be aware that there is the reason in the form and reflect such reason into the reality by looking for such reason. The class of calligraphic theories largely influences the values of calligraphic works in the undergraduate courses. It is, therefore, expected that the utility theory of Unpil would enhance the humanistic values in the education of calligraphy and appreciation of calligraphy as well.