In this talk, we give a proof a theorem states that the Floer homology of a Morse-Bott component is isomorphic to singular homology with a local coefficient system. This is one of the main ingredients of the construction of Morse-Bott spectral sequences for Hamiltonian Floer homology groups. We first explain the case of $_2$-coefficient, and then outline how to construct a suitble local system over a Morse-Bott component for general coefficient cases.