Highway traffic safety is an important area in transportation engineering. Highway intersections are nodes of road networks and accident-prone locations. They are the places where vehicles coming from different approaches and moving towards different directions interact and conflict with each other. Due to the conflicts from all users, more traffic crashes could happen at unsignalized intersection as compared with roadway segments. Popular methods which are based upon traffic accidents and traffic conflicts are proved to be effective in certain circumstances, but difficulty in data collection of traffic crashes and subjective judgment and determination of traffic conflict constrain their applications. This paper introduces an approach to evaluate and improve unsignalized intersection safety performance. This method is fully based on the existing conditions of unsignalized intersection, including geometric design, sight distance, pavement surface conditions, traffic control devices, and lighting, etc. Different from the crash-based and conflict-based methods, this approach is a non-crash and non-conflict based analysis method. This approach needs to go through a field survey to unsignalized intersection to be evaluated. In this approach, a safety index is introduced to give a diagnostic summary of the safety performance degree of unsignalized intersections. Corresponding countermeasures are ranked and recommended based on the cost benefit analysis. In this paper, the approach (called diagnostic approach) is practically applied to evaluate and improve the safety performance of some unsignalized intersections in Fallujah city of Iraq.