This paper draws mainly upon government documents of the Republic of China, the United Kingdom, and the United States of America, to examine the work accomplished and the role played by Wang Pengsheng in intelligence cooperation and integration of the KMT Government. Wang led the Institute of International Relations (IIR) under the direction of Chiang Kai-shek in the beginning of China's all-out war against Japan. He was responsible for collecting international intelligence concerning the strategic status of Burma and India in the midst of intensifying Japanese military advance, and participated in multilateral negotiations among French Indochina, Thailand, British Singapore and Burma. Secondly, this paper examines the involvement of the IIR led by Wang Pengsheng in anti-Japanese propaganda in Burma and India before and after the outbreak of the Pacific War. Finally, it discusses the impact of Wang's activities upon the Nationalist Government's plan concerning its cooperation with the intelligence communities of its allies, mainly the British Special Operations Executive (SOE). It discusses too the internal and external hardships suffered by the IIR during China's political turmoil against the background of the changing power relations between Britain and America. Through these analyses, this paper delineates the practical impact of Wang's work on the Nationalist Government's pragmatic diplomacy during the war as well as explores the characteristics of international political secret service.