Abstract: Due to current limitations in remote sensing principles and technologies, directly determining the true occurrence and precise content of water ice in lunar regolith remains unachievable. In-situ identification of water ice in lunar regolith is therefore urgently required. The Chang’e-7 mission, part of China’s fourth lunar exploration phase, aims to explore water ice at the lunar South Pole. The rover-mounted micro-sampling device, part of the instrument for measuring volatile components in lunar regolith, is designed to perform in situ quantitative sampling. Due to the variability of lunar surface conditions, sampling quality is highly dispersed. Variations in sampling time, soil temperature, and contact force during operation inevitably lead to sublimation losses of water ice. To ensure the reliability of the volatile components detection payload, its in-orbit measurements of water and ice content must be validated through ground-based calibration tests and analytical methods aligned with its operational workflow. This study analyzes the uncertainties in sampling volume and the causes of water ice loss during the operation of the micro-sampling device. A calibration method and corresponding device are proposed to account for both sampling volume and water ice loss. Based on the occurrence characteristics of water ice in lunar regolith, an icy lunar soil simulant was prepared using a gas-phase deposition method, followed by calibration experiments. The results offer practical and feasible technical solutions for detecting and utilizing water ice resources on extraterrestrial bodies, supporting China’s space exploration efforts.