In recent years, several accidents involving container ships have occurred in which the ships capsized when loading or unloading operations in ports, resulting in casualties of personnel, damage to cargo, and huge financial losses. In all cases, the reasons for the accidents were found to be operational errors causing the ships to tip sideways owing to changes in cargo weight. Since the loading and unloading of containers are subject to random conditions, such as the timing of arrival versus the space conditions in the cargo holds and the on-the-spot decisions of operational staff, it is difficult to plan for the effects of cargo weight changes on the ship stability during loading or unloading. However, the general operating environment in a harbor is under a still water condition, and changes in the ship stability can be monitored by detecting the minute rolling periods of the ship. We explore the practicality of monitoring the rolling periods of container ships using a simulation model comprising an embedded system with a nine-axis attitude module; the module is attached to a ship model to record the rolling angles of the ship in a static pool and transmit the data to a computer for analysis. The experimental results show that the embedded system with a nine-axis attitude module as a sensor can be applied to capture the rolling period of a container ship; moreover, it can be applied to analyze the rolling data and obtain optimized relevant ship-stability parameters for loading and unloading operations.