In recent years, America's involvement in South China Sea dispute has become more obvious and assertive, disrupting China's efforts to protect its own rights. Nevertheless, the United States also encounters policy dilemmas in this process, having to take the following issues into consideration: Sino-US relationship, the imbalance between intent and capacity, and the gap between the US and other claimants. In the future, the US may continue to interfere with the dispute under the banner of re-balancing strategy, particularly focusing on rules and regulations. However, the policy dilemma it faces also implies the space for Sino-US cooperation and consultation.