Abstract: As an important mechanism for resolving disputes between investors and host states, the transparency and fairness of international investment arbitration are directly related to the credibility of its rulings and the healthy development of the international investment legal system. This article focuses on the lack of transparency and questions about fairness in investment arbitration proceedings. Through an in-depth analysis of typical arbitration cases, it reveals structural flaws in the current system regarding procedural openness, third-party participation, consistency of rulings, and arbitrator independence. The research shows that excessive confidentiality undermines the public's right to know and procedural oversight, while issues such as the arbitrator selection mechanism and inconsistent application of law erode the fairness of rulings. Although reform measures, such as the UNCITRAL Rules on Transparency, have achieved some success, deep-seated conflicts between investor rights and host state regulatory power, and between efficiency and fairness, remain prominent. As a major source of two-way investment, China should actively promote rule improvement, adopting comprehensive measures in areas such as domestic law integration, arbitrator training, and corporate compliance, to enhance its capacity to participate in international rule-making and contribute to building a more open, fair, and transparent international investment governance system.