The largest library in Guangzhou is definitely a university library, such as Sun Yat-sen University Library, Guangdong University of Foreign Studies Library and South China Agricultural University Library. At least the library of South China Agricultural University where I am located is much bigger than Guangzhou Library and Zhongshan Library on Wen Ming Road (provincial map). Not only is the area large, but the collection scale is not comparable.

In addition, the libraries in the university towns I have been to, such as Sun Yat-sen University, Guangdong University of Foreign Studies, South China Normal University and Guangzhou University of Chinese Medicine, are far larger than the Guangzhou Library and Zhongshan Library on Wen Ming Road (provincial map).

However, university libraries are not open to the public.

If you are talking about public libraries, Guangzhou Library and Zhongshan Library (provincial map) located on Wen Ming Road are already the largest libraries open to the outside world in Guangzhou.