于右任先生（1879-1964）的書學成就，為當今世人所稱頌，其書蹟也被視為現代漢字書法的重要珍寶。不僅在他參與民國革命時，為重要的政治人物角色，其重點在於他對書法的貢獻與推廣，對碑誌文物的蒐集及捐贈，還有推動標準草書的整理等。對於于右任的書學成就，多數會關注到他對於推動標準草書，以及晚年草書風格的表現。然而以書法的藝術情趣觀之，則中年時期所作的行書更覺意趣豐富，此時期將早年帖學能力再融入碑派書法，出帖入碑調合一氣，在行書的結體中融合了魏碑的筆意，使得行書的筆勢運生出渾厚的線條質感，在流暢的行筆當中更顯提按頓挫的節奏。還有時值壯年，經歷過沙場奔馳，筆端間豪情壯志顯露無遺，以其自然無造作之情，得自然之妙意。縱觀其一生書學，莫不對於其晚年草書渾拙天成而大為讚賞，但使得其草書能達到壯闊氣勢的因素，應該是對魏碑文字的臨寫所立下的書寫功力，中年時開展出有碑派味的「碑意行書」，以此厚實的底蘊，再逐步開展出渾圓自然的書風。再加上其氣度超然卓絕，天性豁達的人格影響所致。所以本文以于右任的行書美感特質及其重要性做探討。

Yu Yu-jen (1899-1964) has been praised worldwide for his extraordinary achievements of Chinese calligraphy. His calligraphy works have been highly valued as marvels of modern times. Yu was actually a significant calligrapher and political figure in China. Reformist as he was, he devoted his efforts and time to promoting and donating the collections of standardized cursive script in the hope of demonstrating and preserving the beauty of the calligraphy art. When it comes to Yu’s efforts in calligraphy,critics pay more attention to his promotion of standardized cursive script as well as Yu’s unique expression of cursive script in his late years. However, seen from the perspective of art value, his running script of his middle years presents more complexity and richness. Influenced by what he had learned in his youth, Yu’s running script thereby encompassed two major styles for which he is renowned – modelbook and stele. The impact of regular forms in Wei dynasty steles is evident everywhere in Yu’s running script. It is notable that the lines and strokes Yu brushed are imbued with vitality, ripeness, and smoothness. Each stroke is precise, powerful, and penetrating. Each line and dot form rich variation and express the dynamic spirits of his running script. Moreover, in Yu’s mid-fifties, Yu showed great enthusiasm for both his political career and calligraphy works. His running script thus highlights a force, or more precisely, a mellow strength, which naturally carries the integrated flow of modelbook and Wei dynasty steles. It is true that Yu’s remarkable running script has been universally recognized. Nonetheless, few people are aware of the importance of the Wei dynasty steles, which in fact cultivates a basis, and further, a deeper understanding of Yu’s cursive script. That is, the Wei dynasty stele helps Yu advance the essence of an overall, dynamic force which is consistent throughout his cursive script works. In addition, since Yu has a personality in open-mindedness, all these traits and factors pave the way for Yu’s “stele- style running script.” The aim of the paper is to explore the beauty and importance of Yu’s running script.