In this study, a melt-blown nonwoven filter for medical masks was manufactured using an online hydro charging system. The effects of basis weight (gsm) and die to collector distance (DCD) on the breathing resistance and filtration efficiency were investigated. Hydro charging of the nonwoven web seemed to improve the filtering efficiency. However, it did not affect breathing resistance. It was demonstrated that the breathing resistance and filtration efficiency increased with increasing gsm but decreased with increasing DCD. With a DCD of 19 cm, when the gsm increased from 20 to 50 gsm, breathing resistance increased from 5.14 to 8.33 $mmH_2O$ and filtration efficiency increased from 81.39 to 94.98%. With a basis weight of 25 gsm, when the DCD increased from 15 to 25 cm, breathing resistance decreased from 7.38 to 4.27 $mmH_2O$ and filtration efficiency decreased from 89.56 to 68.28%. In addition, it was demonstrated using stability tests that the hydro charging effect lasted for 13 weeks.