(Fe0.6Co0.4)86Hf7B6Cu1 nanocrystalline alloy obtained in isothermal annealing process from amorphous precursor was investigated as candidate of soft magnetic materials for high temperature applications. Co substitution for Fe can enhance the curie temperature of amorphous alloy (Tc = 630 ℃) and improve the magnetization of nanocrystalline alloy at high temperature ( ≈ 1.56T at 550 ℃). After annealing amorphous precursor at 550 ℃ for 1 hour, the optimum nanocrystalline alloy can be obtained which shows the local minimum coercivity ( ≈ 16 A/m). The coercivity increases with the increase of annealing temperature corresponding to the formation of ferromagnetic phase in the secondary crystallization. Furthermore, additions of Hf and B elements reduce the melting temperature of the alloy studied comparing with the Fe-Co binary alloy.