Influenced by the civil wars and disorder, piracy problems in the 1920s had reached one of the climaxes in the history of modern China. Foreign shipping and trading activities were threatened by pirates. Among these pirates, those came from the Bias Bay near Hong Kong were the most notorious and rampant. Having attacked foreign ships navigating in the southeast China waters, they took ships to the Bias Bay, and fled to the inland with hostages and booties. Britain, the US and other foreign powers all loathed these Chinese pirates and pondered what to do next. Compared and contrasted to Britain’s aggressive attitude toward these piracy problems, the US’s reaction deserves a closer look, as it was very conservative and cautious. Perhaps, it was due to the reason that her shipping interests in China were not threatened directly by pirates, the US tended to adopt an outsider’s approach with a calm observation on how the Britain dealt with the problems. Besides, featured by its humanitarian tendency in foreign policy, the US was reluctant to resort to force in case any military actions might have caused civilian casualties. The US thought that Britain’s ways of suppressing pirates were too radical to be accepted. That’s why the US usually refused to cooperate with Britain and maintained a limited anti-piracy operation. On the other side, the US could not have avoided her obligation in antipiracy affairs in fact. Although the US shipping companies were not threatened by Chinese piratical attacks directly, her business activities in China at large still might be affected by these pirates. American businessmen travelling between different ports along southeast China mainly relied on other foreign shipping companies, especially the British ones. In other words, American business and travelling security in China were protected by the British. Thus, though the US might not have accepted the reasons of the British proposal to work together against Chinese pirates, it felt the emotion that she also had the obligation to share the burden for dealing with these pirates. Such contradictory mentality of the US was also reflected in the later controversy over an international suppression of Chinese pirates brought up by the Diplomatic Body in Peking. As the British diplomat there proposed a memorandum of international cooperation plan for curbing piratical activities in their diplomatic conference, the American diplomat did express his agreement on the importance of an international cooperation to suppress Chinese pirates and promised to work on American government’s endorsement. However, this issue aroused a serious policy argument within the US Government, and the State Department called a halt and doubted the feasibility of the plan. Though the American diplomat tried to persuade the Department and claimed that it was proper and advantageous for the US to join the cooperation, the Navy and the Division for Far Eastern Affairs both had very different views and declared their stands against the plan. The Secretary of State sided with the Navy and the Division and finally decided to reject the proposal. American objection caused such a chain reaction that both France and Italy decided to follow, and withdrew their previous supports, which was a fatal blow to Britain’s cooperation plan. This research analyzes contentious views within the American government, especially the discrepancies between the State Department, the legation and consulates in China, and the Navy. By means of clarifying the inter-departmental and intra-departmental contentions, and interpreting them under the context of Washington Conference System, we may have a better understanding of American idealism and her adaption to any real situations.