This paper focuses on how to use IoT technologies to monitor the project implementation process in prefabricated building (PB) construction, which will help optimize the construction schedule and ensure the quality and safety of PB construction. Although IoT monitoring can obtain a large amount of data during construction, the challenge is how to convert these data into intelligent information needed for feasible decision-making. Therefore, we need to clarify the key factors requiring monitoring during construction and how to use these data to make decisions. In this paper, we analyze the whole process of PB construction, comprising five phases: pre-construction, off-site manufacturing, delivery, on-site assembly, and finishing. Through mathematical model formulation to discover the key factors that affect the construction implementation process, we clarify the monitoring data that need to be obtained by IoT technologies. Using these monitoring data, it is possible to make judgments on process abnormalities, promptly give alarms, make proactive adjustments, and optimize the construction implementation process, thus achieving the goal of ensuring project quality and construction safety.