Su Shi's letter to Xie Minshi ”Yu Xie Minshi Tui Guan Shu” was written in 1100, one year before his death. The contents gave an account of prose writing; he brought up literary concepts of ”Wenli Ziran” and ”Cida” in this letter. He feels that literary works should be a reflection of the objective world, natural and diverse. ”Cida” refers not just to grasp of the main theme of the writing and clarity in expression but also to the style of language used. This letter may be considered as the essence of his lifetime work pertaining to prose writing. The letter is now in the possession of Shanghai Museum. On the back of the scroll is written, Chen Jiru and Dong Qichang's comments and analysis amongst others, of his calligraphy. This paper explores Su Shi's views towards prose writing, the ”Cifu” ancient style of writing as well as his bold and restrained style of writing prolific in his literary creation and calligraphy. It is attempted from various angles such as the letter contents and calligraphy styles.