Multifractal spectra provide a way of encapsulating information about the nature of random measures living on the boundary of a Galton-Watson tree. In this thesis we investigate the ;tal spectrum for various harmonic measures. These are the hitting distributions of various random walks on the Galton-Watson tree. We use martingales and change of measure techniques for calculating Hausdorff dimension to establish the spectra. We also investigate a multifractal spectrum for the interaction between visibility measure and the branching measure.