[Background] Porcine epidemic diarrhea virus (PEDV) is one of the major pathogens causing diarrhea in piglets. The rapid onset makes it difficult to document the cases, and few studies have reported the dynamics of PEDV distribution in pig farms after PEDV infection in piglets. [Objective] To explore the transmission dynamics of PEDV in large swine farms and improve the strategy for the prevention and control of porcine epidemic diarrhea (PED). [Methods] The transmission process of PEDV after infection in piglets in a closed large farm was simulated and the virus abundance in piglets and different areas of the farm was determined. [Results] The virus abundance of anal swabs and air samples presented consistent changes in the early stage of PEDV infection in piglets. The spread of PEDV in the farm was closely related to the movement of employees, and the bathing room might be a major hiding place of PEDV. [Conclusion] The virus abundance in the air of swine barns has the potential to be used as a monitoring indicator in the early stage of PED, and employee-associated media and sites are key targets for the prevention and control of PEDV. This study provides a reference for improving the control of PED and lays a foundation for research on the spread of similar viruses in large pig farms.