In the context of space missions, extensive ground testing is conducted to ensure functionality and performance before launch. The gravitational reference sensor, crucial for the quality of detected gravitational wave signals, relies on a critical payload known as the test mass. Meanwhile, the grabbing, positioning, and release mechanism manages the injection of the test mass from a caged configuration into a free-falling state. It is essential to characterize the dynamic behaviors of the test mass during release, with stringent constraints on residual momentum. Seven working modes—test, launch, release, calibration, scientific, recapture, and standby mode—are proposed by this paper, for the aforementioned mechanism. These modes complement each other to address all potential situations and emergencies in space. Building on these seven modes, this paper also introduces a hardware-in-the-loop simulation method, combining physical mechanisms and algorithms to address the congruity between ground and space conditions. Evaluation methods are presented to optimize and iterate the parameters for each working mode.