Abstract: The planar honeycomb graphs consist of equal regular hexagons. Using the concept of He-matrix corresponding to characteristic/dual graph of honeycomb graph, we present various properties of spectrum which include lower and upper bounds. Moreover, number of negative and positive eigenvalues is related to the maximum number of pairwise non-adjacent edges and the maximum number of pairwise non-adjacent vertices of the planar honeycomb respectively. Some open problem will also be discussed.