In this work, nanoporous carbon was synthesized from direct pyrolysis of ZIF-8, and the capacity fading of nanoporous carbon anode was explored. The structure, crystal phase, pore texture and elemental bonding were characterized by using scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption and X-ray photoelectron spectroscopy, respectively. When employed as anode for lithium ions batteries, the nanoporous carbon derived from ZIF-8 owns outstanding discharge capacity of 3164 mAh/g during the first circle. However, the charge capacity fades to 1347 mAh/g and the reversible capacity is only 42.57%. We have found that the structure damage and irreversible alloying reaction during insertion-desertion of lithium ions are responsible for this phenomenon. Innovatively, introduced density functional theory provides crucial proofs about capacity mechanism for N-doped graphene based nanoporous carbon anode of lithium-ion batteries.