C-HRA-5(22Cr25Ni3Cu4W2Co) is a new kind of austenitic heat-resistant steel with excellent combination of high temperature strength and resistance to high temperature steam oxidation, can be used for the superheaters and reheaters (with the highest temperature 700℃) in the advanced ultra supercritical (A-USC) boilers. Compared with the existing austenitic steels, as HR3C, Super304H, TP347, the alloy design of the investigated steel is more complex. The precipitation of second phases will affect the mechanical properties of the steel. As known, the Cu element precipitated as Cu-rich phase in the Super304H steel; the Nb element precipitated as Z phase in the HR3C steel, but as Nb-rich MX phase in the Super304H steel. However, the precipitation and evolution of second phases in the C-HRA-5 steel has not been investigated clearly. In this work, the C-HRA-5 steel specimens were aged at 700℃ for 0~15627 h. OM was used to observe the changes of grain size and twins, and the evolution of the second phases in aged specimens was analyzed by SEM+EDS and TEM+EDS+SAED. The results are as follows. The grain size of the investigated steel was stable, and the second phases precipitated during 700℃/15627 h aging, including Z phase, Cu-rich phase, Laves phase, and M23C6 carbide. M23C6 mainly precipitated on the grain boundaries, the others in the grains, but σ phase was not founded. During aging, the Z phase and Cu-rich phase were relatively stable, especially the average diameter of the Cu-rich phase was less than 10 nm after aged for 15627 h. These phases are the main factors increasing the strength. The coarsening rate of M23C6 carbide on grain boundaries was fast. After aging for 817 h, the network of M23C6 carbide was observed on grain boundaries. After 15627 h, the width of M23C6 carbide was about 550 nm. However, the coarsening rate of the M23C6 inside grains was slow. In the late-stage of aging, due to the addition of W, a large number of needle-shaped Laves phases precipitated inside grains. And the coarsening of Laves phase was apparent in length but slight in width. A small amount of granular Laves phase precipitated near or in the M23C6 carbides that on grain boundaries and its size was stable. During the long-term of aging, no σ phase was found. It is because that the high content of Ni and addition of Co could inhibit or delay the precipitation of the σ phase in the C-HRA-5 steel.