The purpose of this thesis is to answer two research questions: firstly, what was the relationship between China’s modernization and the changes in citizen diplomacy from the 1920s to the 1940s? And secondly, why was the relationship between China’s modernization and the changes in citizen diplomacy in this period negative? I contextualize the term “modernization” and provide an overview of China’s modernization firstly. Then I define citizen diplomacy in the context provided by the previous sector. Also I compare it to other similar conceptions, such as “track two” diplomacy and public diplomacy, to deepen the understanding of citizen diplomacy. I go on to consider how China’s modernization evolved, compared with the changes in citizen diplomacy from the 1920s and 1940s: a negative relationship between the two variables is presented. I clarify the correlation of modernization and democratization of diplomacy in order to explain the negative relationship in the Chinese context.