Xue Yunsheng (薛允升) was a prominent legal scholar of the Shaanxi School during the Qing Dynasty (1644-1912 AD). He compiled Doubts on Reading the Substatutes with the aim of revising and improving the Great Qing Code. In this work, he systematically identified problems within the substatutes of the Code, primarily including inconsistencies between substatutes and statutes, contradictions among different substatutes, discrepancies where substatutes aligned with neither the statutes nor the overall legal framework, as well as conflicts between earlier and later substatutes or among parallel provisions. While pinpointing these errors, and guided by the legislative principle that laws should be concise and uniform, Xue proposed specific recommendations for deletion, consolidation, and revision. Doubts on Reading the Substatutes exerted significant influence on the legal developments of the late Qing and early Republican periods, particularly on the drafting of the Great Qing Current Criminal Code.