Abstract: There is a fragmented red grid manuscript of Catalogue of Siku collected in Nanjing Library. It is written in ink, style of Gong Kai, official script, and proofread in red and black. Its number of lines and words is in line with the original copy of the Siku. The author compares it with four copies: the manuscript of Catalogue of Siku revised by Ji Xiaolan in Tianjin Library, the original manuscript of the Siku by Wenyuge, the copy of Zhejiang and the copy of Wuyingdian. It is found that the copy of Zhejiang is consistent with the copy in Nanjing Library, but different from the manuscript of Wenlan and Tianjin Library. In particular, given that some irrelevant and unattended texts in the copy of Zhejiang are the same as the copy of Nanjing Library, but different from the other copies, it can be confirmed that the copy of Nanjing Library is the base of the copy of Zhejiang. It is further proved that the copy of Zhejiang was not based on the manuscript of Wenlan, nor its other copies annotated with text, but based on the original Catalogue of Siku written by Siku Museum. The copy of Zhejiang is a collection, proofread on the transcript of Wenlan, and included the proofreading of Lu and Wang