A facile, low-cost and green ultrasound-assisted method was developed to ultra-fast synthesize Mn3O4 nanosheets supported on reduced graphene oxide (RGO). Such hybrid materials exhibited ultrahigh performance as lithium ion battery (LIB) anodes, whose specific capacity reached more than 1400 mA h g(-1) after 40 cycles at a current density of 100 mA g(-1) (based on the mass of Mn3O4). The remarkably enhanced LIB performance could be attributed to their layer-by-layer aggregation structures.