Fe61Co39 nanoparticles were prepared by hydrogen plasma metal reaction. The as-synthesized nanoparticles were characterized by x-ray differaction (XRD), transimition electron microscope (TEM) and superconducting quantum interference device (SQUID). The nanoparticles are spherical in shape, have bcc structure with the mean particle diameter of 41 nm, and are basically ferromagnetic with a slight amount of superparamagnetic part. The saturation magnetization and coercivity of the nanoparticles at 4.2 K are 190.15 emu/g and 1280 Oe, respectively. The blocking temperature is 250 K in 100 Oe and decreases with increasing the magnetic field.