于右任研习书法碑帖并重，其行书作品相较于楷书有着更为明显的碑帖融合特点，相较于草书有着更早的碑帖融合实践。本文以于右任的行书艺术为研究对象，梳理其行书风格发展脉络。于右任的行书创作可分为四个阶段：早期继承帖学传统，学习二王、赵孟頫，流畅自然。后广泛开展寻碑活动，受到六朝墓志影响，在劲俏挺拔的楷书样貌基础上，融入行书笔意，初步形成碑体行书样貌。中年研究视野扩及摩崖、造像，并汲取篆隶营养，书风转为雄浑开阔，碑体行书逐渐成熟。晚年受草书的线质和结构影响，碑帖融合愈发自然，碑体行书达到平淡中和的境界。于右任的行书植基于魏碑，但并不刻意追求方峻与生涩，而是化去刀痕，在畅达自然中展现出高古、开阔、自由的境界。清代以来对碑体行书有各种探索，于右任的行书与赵之谦、康有为等前辈大家相较，既有共性也有鲜明的个性，卓然自立。他的行书具有高超的艺术格调，更蕴含了高尚的民族情怀与革命精神，为学书者带来多方面的启示。

Yu Youren’s calligraphy notably integrates steles and manuscripts. His running script shows clearer stele elements compared to his regular script and earlier integration than his cursive script. This article explores Yu Youren’s running script development. His calligraphy evolved through four stages: early years adopting traditional scriptural studies, learning from the Two Wangs and Zhao Mengfu; extensive stele explorations influenced by the Six Dynasties, blending robust regular script with fluid running script traits; mid-life expansions into cliff and Buddha inscriptions, incorporating seal and clerical scripts, leading to a bold, expansive style; and later years, influenced by cursive script’s line quality and structure, achieving a balanced, natural integration of steles and manuscripts. Rooted in Wei steles, Yu’s running script eschews deliberate harshness, instead smoothing over the knife marks to reveal an ancient, open, and free expression. His unique style, distinct from predecessors like Zhao Zhiqian and Kang Youwei, combines artistic excellence with deep national and revolutionary sentiments, offering rich insights for calligraphers.