Graph operations play an important role in many application of graph theory because many large graphs can be constructed from small graphs. Here we study two graph-theoretical operations, i.e., the double and the strong double graph. In the organic compounds alkanes are least reactive and simplest hydrocarbon that contains of hydrogen (????) and carbon (????) atoms and have no any other functional groups. In this paper, we computed the topological indices, namely, Inverse sum indeg index (????????????), first multiplicative-Zagreb index (????????1), atom bond connectivity index (????????????), forgotten index (????), geometric arithmetic index (????????), second multiplicative-Zagreb index (????????2) for the double and strong double graph of alkane ????????????2????+2. In addition, we also give a graphical and numerical comparison of these topological indices.