A series of Co-zeolite samples were synthesized at 170-200degreesC, controlling the reaction between a Si-Al-Co hydrous oxide and NaOH solution. With increase of the reaction time, and NaOH concentration, synthesized phase changed in the sequence of MOR, PHI, and ANA with Na. The results of chemical analysis and FT-IR spectra of each phases showed that NaOH concentration in the initial slurry and the architecture of zeolite affected Co fixation in the zeolite structure.