The time required to implement projects is one of the basic elements for evaluating the performance of these projects, as the project is considered successful if it is delivered on time, and there are many and multiple reasons that lead to delay in the project time. Delay in time is considered one of the important problems that affect the performance of projects. This research aims to know the role of the structural systems used in the construction of multi-storey concrete buildings in reducing construction time and thus reducing the total time required to implement projects. A group of structural systems commonly used locally in the city of Mosul were applied, such as (1-Traditional building system -in-situ pouring of concrete 2-The Tunnel system and 3-The prefabricated system -pre-casting of concrete, in addition to 4-A proposed system within the study, which is a combination of 1 and 3) on a model of a multi-storey residential project, in view of the great need for residential units and the importance of implementing them at an appropriate time compared to the cost achieved from that. This can be considered the optimal time for implementation while maintaining the necessary efficiency for these projects. To test the research hypothesis which states that the construction system has an important role in achieving the optimal time for project implementation, the data obtained from each system was extracted and compared, then the completion rates for the first 100 hours of work were calculated. In an attempt to determine the system that achieves the optimal time required for construction, it was concluded that it is difficult to determine the optimal system directly, but it can be considered that the prefabricated building system can be considered the optimal system on the one hand, and the time and Mixed System can be considered the optimal system in terms of cost, and the results. The study may help decision-makers who are specialists in the construction industry to take appropriate measures and determine the appropriate construction system in constructing projects.