In this study, porous micrometer-sized MnO cubes have been designed and synthesized by hydrothermal treatment followed by high temperature annealing. The pore size is controlled by changing annealing temperature in order to achieve good electrochemical performance. The cube edge length is about 10μm and the pore size changes from mesoporous to macroporous. The presence of pores in the MnO cubes is able to accommodate the volumetric changes during electrochemical cycling, and enables electrolyte easy penetration so that to improve the electrochemical performance. The porous micrometer-sized MnO cubes prepared by hydrothermal treatment at 100°C followed by annealing at 700°C delivers the best long-term and rate cyclability owing to its stable porous structure serving as lithium ion rapid transfer channels and enough pore volume to accommodate volumetric changes during electrochemical cycling. The reversible capacity in the first cycle is 615.9mAhg−1at 0.2Ag−1, slightly decreases to 404.6mAhg−1 at 1.0Ag−1in the 6th cycle and remains at 425.5mAhg−1 at 1.0Ag−1 even after 495 cycles. The same porous micrometer-sized MnO cube electrode delivers high rate reversible specific capacities of 201.8 and 50.4mAhg−1 at 5.0 and 10.0Ag−1 respectively.