Slicing is an important decomposition technique for program understanding. However, traditional slicing methods tend to produce too large slices for human inspection as modern programs are often huge and static program analyses are hard to be precise enough. One possible solution to such problem could be combining other program decomposition techniques together with program slicing. With such inspiration, this paper proposes a scenario oriented program slicing method to slice programs under specified execution scenarios. The scenarios provide a clear and easy understanding functional decomposition for the system, while the new slicing method can help figure out how a computation is implemented in a given scenario by effectively reducing the amount of code that a user needs to inspect.