Abstract: Cu-1.9Be-0.25Co alloy was treated by solid solution treatment at 780℃ for 4 h and aging treatment at different temperatures(300, 320, 340, 360℃) for different holding times(1, 2, 4, 8, 16 h). The effect of aging on the precipitation behavior of the alloy was studied. The results show that the peak aging process was 320℃×8 h, and the hardness of the alloy under this process was 422 HV. The evolution of precipitates in Cu-1.9Be-0.25Co alloy during aging at 320℃ was metastable γ' phase → semi-coherent γ' phase → non-coherent equilibrium γ phase. A large number of precipitates in the early stage of aging (1-2 h) in a short time was the main factor for the rapid increase of alloy hardness. The semi-coherent relationship between precipitates and copper matrix in the middle of aging (2-8 h) was the main reason for peak aging. At the later stage of aging (8-16 h), the precipitates separated from the semi-coherent relationship with the matrix, the alloy was over aged and the hardness decreased.