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In order to study the effect of Zr on the microstructure and isothermal annealing performance of Cu–Cr in situ composites, Cu–15Cr and Cu–15Cr–0.24Zr alloys were prepared by means of vacuum medium frequency induction melting technology. The two kinds of test alloys with deformation of 3.79 were subjected to isothermal annealing test. The effects of Zr on the as-cast microstructure, the isothermal annealing structure and the tensile fracture morphology of Cu–15Cr alloy were studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The results show that the addition of Zr leads to the formation of homogeneous and fine CuZr intermetallic compounds, which suppresses the formation electron microscopy of eutectic Cr phase and makes the eutectic Cr content much lower than that of Cu–15Cr alloy. The recrystallization temperature of the Cu matrix is increased, and it is maintained at a fine equiaxed crystal at 400 ℃. After isothermal annealing at 400 ℃ for 220 h, the tensile strength, electrical conductivity and elongation of the test alloy containing Zr were 720 MPa, 68% IACS and 6.7%, respectively; while the tensile strength, electrical conductivity and elongation of the test alloys without Zr were 488 MPa, 70% IACS and 12.4%, respectively.