The temperature and humidity distributions in a pharmaceutical warehouse affect the efficacy of the medicine stored in the warehouse. For a stereoscopically-monitored high-rack medical cold-storage unit in Tianjin, the influence of shelf layout on the temperature and humidity distributions is examined. The internal airflow distribution of the cold storage unit is optimized. Using the field synergy theory, the temperature and humidity distributions, temperature and humidity uniformity, and refrigeration effect are systematically discussed. Based on the findings, the field synergy angle can be effectively used to evaluate the performance of a high-rack cold storage unit. Increasing the spacing between the shelf layers optimized the unit's thermal performance. At a shelf-layer spacing of 0.6 m, the average temperature, the temperature inhomogeneity coefficient (K_t), average relative humidity, relative humidity inhomogeneity coefficient, and the average field synergy angle (α_p) were 4.56 ℃, 0.039, 55.21%, 0.015, 57.47°, respectively, resulting in a more uniform and reasonable temperature field.