Does RAKE receiver need channel equalization under Ultra Wideband (UWB) multipath channel with inter-symbol interference (ISI)? The conclusion has not been explicitly drawn up so far. By considering the ISI as AWGN in RAKE receiver, or the channel delay spread being reduced by RAKE receiver, researchers hold the optimistic argument that RAKE receiver can play the role of equalization. This paper investigated these existing viewpoints. By analyzing the conditions and foundations from which the controversy originates, we also theoretically studied the performance of RAKE receiver under ISI. The RAKE receiver and equalization simulations, where the multipath channel models under IEEE 802.15 standard were adopted, were designed to validate the analysis. It comes to the opposite conclusion that RAKE receiver does not have the ability to suppress ISI. Therefore, it needs channel equalization to tackle ISI under UWB multipath channel environment.