Functioning of business processes of high-tech enterprise is in a constant interaction with the environment. Herewith a wide range of such interaction represents a variety of conflicts affecting the achievement of the goals of business processes. All these things lead to the disruption of functioning of business processes. That's why modern enterprises should have mechanisms to provide a new property of business processes - ability to maintain and/or restore functions in various adverse effects. This property is called Functional Stability of Business Processes (FSBP). In this paper, the authors offer, showcase and test the new approach to assessing the results of business process re-engineering by simulating their functional stability before and after re-engineering.