Abstract: Japan’s intelligence activities in China were part of the implementation of Japanese colonial policy in East Asia.Prior to the Sino-Japanese War of 1984-95,Japan stepped up intelligence activities with the establishment of agencies in China.Japanese spies who posed as diplomats,businessmen，and students,disguised themselves as native Chinese,or were in fact bought-off Chinese traitors,collected information in all parts of China in order to prepare for aggression against it。After the Sino-Japanese War broke out，Japanese intelligence activities were even more widespread and played a very important role in a series of military campaigns,such as the naval battle at Fengdao Island,the battle over the Liaodong Peninsula,and the battle of Weihaiwei .During the War,some vigilant Chinese officials became aware of the danger of Japanese spies and proposed counter-espionage measures。The Chinese government also succeeded in cracking several spying cases.Generally speaking， however，the Chinese government was not effective at uncovering spies or keeping its military secrets.