The composite material of Ni(OH)(2)/biomass carbon have been prepared by a facile "carbonization-acti vation" procedure from Jackfruit peel and a subsequent water-bathing precipitation process. The biomass carbon material after activation (AC) is constituted of small particles and achieves a large specific surface area of 1602 m(2)/g. After decoration of Ni(OH)(2) nanosheets, the Ni(OH)(2)/AC composites were investigated the microwave absorption performances in 2-18 GHz. The maximum reflection loss of the Ni(OH)(2)/AC composites reached -23.6 dB at 15.48 GHz with a thickness of 6 mm. Moreover, the fundamental mechanism based on conductivity, the polarization and defects is discussed. The present investigation offers a new possibility for the biomass based fabrication of potential microwave absorbing materials. (C) 2018 Published by Elsevier B.V.