NaxC60 and LixC60 are wide theoretically studied systems for hydrogen storage. We recently investigated the hydrogen absorption/desorption of Na10C60 and we found that up to 3.5 wt% of H2 could be reversibly adsorbed/desorbed at 300°C through the formation of NaH and hydrogenated-C60 (fullerane). We propose to investigate with µSR the interaction of Muonium, a light hydrogen isotope, in Li6C60 and NaxC60 (x= 8, 10) at different hydrogenation level and at different temperatures, for understanding the absorption process of atomic hydrogen in these systems.