Abstract To explore the unsafe behavior causes of construction industry accidents is helpful in reducing the possibility of occupational accidents in construction work. The data were collected from the Institute of Occupational Safety & Health, Council of Labor Affairs. Since the occupational accidents are unpredictable, they are closely related to grey characteristics. Based on Grey System Theory, this paper establishes an analysis model for the causes of unsafe behavior in Construction Industry accidents using a grey relational analysis. The present model provides a scientific basis for the management of occupational safety and hygiene in construction industry. The construction industry proprietors are supposed to recognize the reasons causing the accidents so as to devote themselves in the management of preventing hazards, reducing the threat to the labors’ live and properties in construction industry.