Kang Youwei(康有爲) was a philosopher, politician, accomplished calligrapher and an educator of the Qing Dynasty and the Republic of China. He started the study of Confucian classics in early childhood, and read numerous books influenced by his grandfather who was a bibliophile. At age 19, he began to study under a great scholar Ju Chaki (朱次琦. 1807∼1881), and immersed himself in the philosophy of Yuk Guyeon (陸九淵) and Wang Suin (王守仁). He also developed keen interest in natural science and sociology of the west, and harbored great ambition for political reforms. He opposed conventional customs, neo-Confucian authoritarianism, and requirements of the state examination. He submitted an appeal to change the law to Guangxu Emperor seven times, and led the initiative for ‘Musulbyeonbeop (戊戌變法)’, but as it failed, he became an overseas exile for 16 years. He wrote many well-known books, and became a renowned calligrapher of a punggolgyeongbal (风骨勁拔) style that he learned from calligraphy work of Gu Yangsun (歐陽詢). After broadly experiencing yukjobipan (六朝碑版), he abandoned dangin (唐人) and pursued bukbi (北碑) instead. As a result, his calligraphy expresses changes and originality even within a rigorous format, and he reached an original height of his own. In particular, his book ‘Gwanyejussangjeup (廣藝舟雙楫)’, which compiled his theory of bihak (碑学), had a great influence on the world of calligraphy. His calligraphy and theory on calligraphy contributed to advancement of modern calligraphy immensely. In this article, we examined Kang Youwei’s practice of calligraphy and examine its relationship with his theory on calligraphy. Between his ideas and philosophy are found both inherent connection and inherent contradiction. Going beyond discussing limitations of ‘Gwangyejussang jeup’, we also explored how his theory changed in the middle and later periods, as well as contradictions between his theory and practice. Additionally, we attempted to organize contexts of his theory on calligraphy based on the technique and style of his work for comprehensive evaluation. In brush strokes, Kang Youwei advocated use of both straight and curved lines. Particularly, his haengseo (行书) style contains disposition of bukbi (北碑), has strong strokes and bone structures, and exudes an air of strength and beauty due to slanted and steep strokes. His gyeolche (结体) expresses a thick and somewhat wanting shape with massive and heavy strokes. His work maintains tidy, generous, natural and artless style. His jangbeop (章法) has an irregular charm with cheerful, indulgent and valiant air. Combining these, his calligraphy creates a unique air of ‘winning with style and creating beauty with power (以氣為勝以力為美)’. In his later years, convergence of bihak and cheophak was notable in his work. Particularly, his haengchoseo (行草书) style began to show strong personality with a mixture of various styles as it stemmed from wibi (魏碑), added elements of jeonye (篆隶), and evolved into jangcho (章草) and cheophak (帖学). Kang Youwei left numerous writings and works of calligraphy. It is difficult to examine and assess his works of calligraphy and theories due to immense amount of materials. We look forward to suggestions to correct and revise this article from distinguished scholars and readers alike.