in the solar interior and emerge into the atmosphere through magnetic buoyancy. Although both views can explain some observational characteristics, the complicated processes of magnetic structures of filament formation are still not fully understood.

Mechanism of the filament mass supply is another issue for understanding the formation of the filament. It is believed that the materials of filaments originate from low atmosphere (such as from solar chromosphere) [@pik71; @zir94; @son17], which are transported to solar corona either through magnetic forces or thermal pressure forces. Based on observational characteristics and numerical simulations, three popular models have been proposed: injection model [@wan99; @liu05; @cha03; @wan18], levitation model [@rus94; @gal99; @kuc12], and evaporation-condensation model [@ant91; @kar05; @xia11; @xia12; @liu12]. In the injection model, cool plasma in the low atmosphere is forced upward in the filament through sufficient force in the magnetic reconnection. Using the UV and EUV data from *Transition Region and Coronal Explorer (TRACE*), [@cha03] reported that a series of jets and two eruptions events could supply the mass necessary for the formation of a reverse S-shaped filament in active region NOAA 8668. [@zou16] also found that cool material could be injected into the filament spine with a speed of 5-10 km/s 