The paper aims to study the achievements of the old generation of Chinese library scholars represented by Mr.LIU Guojun in northern China and Mr.DU Dingyou in southern China(abbreviated to Northern LIU&Southern DU),discuss their influence on the international library world,and ascertain the communication history of Library Science between China and Japan since the middle of the 1920s.The author used to be a visiting associate professor at Keio University from September 1,