The Office of Xinhua Daily was a publishing organization established by the Central Committee of the Communist Party of China in the Kuomintang-controlled areas during the War of Resistance against Japanese Aggression until the early stage of the War of Liberation. Taking its newspaper publications collected by the Chongqing Hongyan Revolutionary History Museum as research objects and basic data in this study, we used ultra depth-of-field 3D microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, and pH measurement to detect and analyze the fiber composition, filler type, paper-making technique and paper acidity of the samples. Combining relevant historical materials, we found the paper used for newspaper was affected by many factors:the political and economic environment, paper-making techniques, and paper-use strategies. Both machine-made and handmade papers were used:in the early stage (from the founding of Xinhua Daily on January 11,1938 to October 24 of the same year), machine-made white newsprint was used most often; in the middle stage (from October 25,1938, when the office was relocated to Chongqing, until the victory of the War of Resistance against Japanese Aggression), improved handmade paper from Sichuan and Chongqing was gradually used; in the late stage (from the victory of the War of Resistance against Japanese Aggression to the forced closure of the office in February 1947), handmade paper was still used. This study provides reference for the conservation and utilization of the publications from the Office of Xinhua Daily and of similar cultural relics.