Accurate scheduling of project is one of the main fundamentals and essential success factors of the project management and also accordance of planning and implementation is considered as the main subject of project management. In this paper, it is tried to propose a practical and suitable system in order to schedule various projects more accurately. Currently Program Evaluation and Review Technique (PERT) is used extensively for management of large- scaled projects. In traditional methods of PERT technique, implementation time of each activity is obtained in the form of definite figures or through Beta Distribution but in the real world; it is very hard to estimate the practical implementation time of each activity in an accurate way. By using fuzzy logic in order to overcome the problems related to uncertainty, fuzzy expert system is designed which many limitations and factors affecting the project completion time have been considered in this article. In this regard, output and input parameters of the system have been acquired by questionnaire and validation of the results has been analyzed. The obtained results indicate high power of the system in controlling different situations affecting the project completion time.