Assessment of the joint strike plan is a pivotal task for planning and decision-making, and it plays a crucial role in selection and employment of operational art. The challenge is how to model the mapping from plans to mission effectively in uncertain situation. Simulation system is inefficient in evaluating plans, while analytic models are unable to reflect the interaction and overall effect of the target system. The probability reasoning models have currently been utilized extensively in the assessment of military operation, and the typical model is Timed Influence Net (TIN). Stochastic Timed Influence Net (STIN) is an extensional version of TIN that has enhanced the description of uncertain delay in TIN. Thus, the method of STIN based joint strike plan assessment was provided. Finally, a numerical experiment was presented to demonstrate the effectiveness of above method.