Amorphous　iron　alloys　nanoparticles　containing　low　content　of　oxides　were　prepared　in　ethanol　medium　by　reduction　of　transition　metal　iron　cation　with　sodium　borhydride.　Mercury-based　ferrofluids　were　obtained　by　dispersion　of　the　nanoparticles　in　mercury.　The　compositions,　sizes,　phases　of　alloy　particles　and　the　saturation　magnetization　and　stability　of　the　ferrofluids　were　characterized　by　AAS,　TEM,　XRD　and　magnetic　balance,　respectively.　The　title　iron　alloy　nanoparticles　is　with　approximate　size　of　12　nm,　16400　kA/m　saturation　magnetization.　Iron　alloy　nanoparticles　with　low　content　of　oxides　are　not　easy　to　be　oxidized　so　they　have　strong　metallic　surface　and　prone　to　disperse　into　mercury　to　form　mercury-based　ferrofluids.　The　ferrofluids　have　210　kA/m　saturation　magnetization　and　strong　anti-oxidation　stability.