The present paper reports the synthesis of the high capacity NiOOH through oxidization of spherical Ni(OH)2 by utilizing high-density NaClO-NaOH solution. The relationship between the structure and the change in electrochemical behavior during the synthesis process of NiOOH was investigated by means of the tests of FSEM, XRD, CV and galvanostatic discharge method. During most oxidizing time, the increment of NiOOH capacity is in linear relationship with the reaction time and is restrained by surface area and the diffusion of protons in solid phase. The optimal reaction time to synthesize ideal spherical NiOOH is 3h. The appearance of a small platform at 1.2V in discharging process and the cracks detected by FSEM of NiOOH during reaction process are the evidence of complete oxidization of spherical Ni(OH)2.