Abstract: As space exploration enters the era of commercialization, an increasing number of private investors are actively participating in various space investment activities. However, due to the systemic deficiencies present in both international investment law and public international law, many space investment activities are effectively left without adequate protection under existing international investment treaties. Specifically, within international investment treaties, the uncertainty in the satisfaction of qualified investments and the inability of substantive treatment clauses to meet the practical needs of space investment activities are notable shortcomings. In public international law, issues such as unclear jurisdiction over specific space activities by host countries in both airspace and outer space further compound the problem of unclear regulatory frameworks. These deficiencies also hinder the effective protection of space investment activities under international investment law. The international community should prioritize the interplay between international investment agreements and public international law, promptly improve systemic deficiencies, and thereby achieve effective protection for various space investment activities.