The drop tower facility generates a ground-based microgravity environment, functioning as a validation platform for a wide range of microgravity scientific experiments. To satisfy the ultra-low microgravity requirements for ground testing of the Gravitational Reference Sensor (GRS)—the core payload of the “Taiji-1” mission—a newly designed experimental capsule was developed for the Drop Tower Beijing (DTB). Using this capsule, successful tests were conducted on the GRS engineering model. Experimental results show that the Test Mass (TM) is stably captured during the effective microgravity period, achieving a control precision better than 1 × 10⁻⁶ g₀/Hz^1/2 across the 1–50 Hz frequency band. Collectively, these results validate both the capture and control performance of the GRS and the capability of the DTB with the newly designed dual-cell capsule to provide a µg₀-level microgravity environment. This successful verification provides strong support for future scientific experiments demanding ultra-high microgravity level.