This study focuses on one aspect of China's labor movement--the relationship between trade unions as a societal force and state power as a political force in the pre-1949 and post-Mao reform years, illustrating that this relationship was characterized by alliance and rivalry and that unions, instead of being tools in the hands of political parties, represented the basic interests of workers and therefore demonstrated a considerable popular character. Chinese trade unions have been closely connected to state and other political forces. These forces needed workers' support in consolidating or striving for state power and therefore regarded it imperative to become involved in labor mobilization, particularly in organizing trade unions. Their involvement partly accounted for the proliferation of various labor organizations, including "signboard" and "yellow" as well as "red" unions, in the pre-1949 years. Such involvement also helped to shape unions' character and functions and gave them certain political orientations. However, political authorities or parties, whether warlord or GMD or CCP, were not able to transform unions into pure instruments of partisan struggles, due to contradictions, competition, or mutual check among these political forces. Competition also existed between different factions within a certain regime, such as the struggle between the city party branch and city government within the GMD. The political parties' aspiration for overriding their rivals compelled them to cultivate confidence of workers as a social group and, for this purpose, they had to show consideration for labor problems and interests, which in turn made it possible for unions to maintain some popular character and a certain degree of autonomy no matter whatever their political orientations. On the other hand, workers seem not so passive as to be easily manipulated by politicians. Having a keen sense of their own distinct interests (primarily economic), they would chose to support only those political parties that offered them the most and join and defend unions that best represented them. The restraints on the power of political authorities or forces and the ability of laborers to make choice and the possibility for them to do so determined that the union-state relationship could be a partnership or alliance. While political forces including state had to use trade unions as an ally, they also regarded the latter as a rival and a potential challenge to their efforts to monopolize and consolidate power. Therefore, every dominant political party or state power-holder attempted to harness trade unions and limit the scope of their activities.