In Singapore, the construction industry had implemented safety management system (SMS) and SMS auditing for about 10 years now, but the improvement in safety standard is not significant. In response to the need to improve the effectiveness of SMS and SMS audit, the aim of the paper is to propose a method to develop and test the tools that auditors may use to assess the effectiveness of a construction firm's SMS. The research methodology adopted in this study consists of 15 steps. Surveys were conducted; safety experts were consulted and invited to express their views, either through interviews or workshops. The Analytic Hierarchy Process (AHP) and Factor Analysis were used to assist in identifying the most crucial factors and attributes affecting safety. The model was developed by means of the multi-attribute value model (MAVT) approach. It was also subject to validation via site audits. Using the model, a Construction Safety Index (CSI) can be calculated. It is concluded that the CSI can act as an objective measure of different sites for management and appraisal purposes.