Fe-0.6%Cu alloy was irradiated with H ions to 0.1 dpa, and then annealed for 30 min from 150 degrees C to 500 degrees C. We focused the evolution of Cu precipitates in irradiated Fe-0.6% Cu alloy after the isochronal annealing from the perspective of positron annihilation. The Delta W parameters after thermal annealing (400 degrees C and 500 degrees C) were much larger than that induced by 0.1 dpa H irradiation. Annealing could promote the aggregation of the Cu-vacancy complexes, and form the Cu cluster-vacancies complexes. When the vacancy-like defects recovered around 500 degrees C, it meant the formation and growing of the defect-free Cu precipitates. (C) 2016 Elsevier B.V. All rights reserved.