Provided are a soft magnetic core having an excellent high current DC biased characteristic and an excellent core loss characteristic and a manufacturing method thereof. The method includes the steps of: after classifying nanocrystalline grains obtained by grinding metal ribbons prepared by using a rapid solidification process (RSP), mixing alloy powders so that a particle size distribution is configured to have a particle size of 75˜100 μm with 10˜85 wt %, a particle size of 50˜75 μm with 10˜70 wt %, and a particle size 5˜50 μm with 5˜20 wt %, to thus prepare the soft magnetic cores by using nanocrystalline alloy powders having an excellent high current DC biased characteristic and an excellent core loss characteristic.