Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from. In case of catalysts synthesized by co-precipitation method, which have active species un-used in bulk phase, can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated catalysts. In this work, the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO + CO reaction. It is found that the deactivated catalyst can be re-generated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.