The methodology of risk calculation for project network techniques is presented. Development and research work is connected with uncertainty and risk. Many models for engineering design process are described in literature but it is necessary to develop a new one which would involve uncertainty. In project management there is much imprecise information based on experts knowledge, such as probability of planning events. Most real-world probabilities are far from being precisely known or measurable numbers. Transitions from precise probabilities to imprecise probabilities in probability theory are a form of generalization. In particular, a probability distribution may be described in words as likely or unlikely. Risk was determined by linguistic variable in the proposed methodology. Type II fuzzy set was used to model the effects of uncertainties in risk determination in project scheduling because of a few experts being concerned with the project. A new graph reduction method for fuzzy graph (graph with fuzzy weight) has been elaborated. It is useful for risk calculation defined by linguistic variable in research and development project planning. The new methodology was illustrated by two examples.
