Recently, an Environmental Management System (EMS) has been used to promote effective environmental protection. Environmental Performance Assessment (EPA) is a critical tool of the EMS in checking, reviewing, monitoring and evaluating environmental performance of organizations. To implement EPA, the relations between Environmental Operational Indicators (EOIs) used in EPA and Environmental Performance Indicators (EPIs) are required, which, however, are lacking in the construction industry. This paper attempts to develop a series of EOIs and EPIs of individual construction projects for EPA and to measure their relations by using least-squares fitting and robust fitting methods. The results show that the defined EOIs correlate strongly with EPIs. Therefore, EPA can be used to identify areas for continuous improvement, and also can provide an early indication of the environmental performance for an organization.