at different moments. (c) The line-of-sight magnetic fields from $SDO$/HMI. White patches denote the magnetic field with positive polarity, while black ones denote the magnetic field with negative polarity. (d)-(f) The corresponding 304 $\rm\AA$ images observed by $SDO$/AIA. \[fig1\]](figure1.eps){width="\columnwidth"}

Fig.\[fig2\] shows numerous cool plasma ejected into the filament height by a series of jets. Panels (a1)-(a4) and (b1)-(b4) exhibit formation process of the filament in H$\alpha$ images. A series of jets occurred in the vicinity of the south-western footpoint of the filament. Accompanying the appearance of these jets, the cool plasma was lifted into the filament height and some of them became the filament material. Two filamentary structures could be identified in panels (b1)-(b4), which are marked by the black arrow and the blue one. The plasma injected by the jets went along the magnetic field lines in the filamentary structure marked by the blue arrow and then fall down to anther footpoint, while the plasma could remain in the filament structure marked by the black arrow. Eventually, the filamentary structure marked by the black arrow became the maturing filament (see the panel (f) of the Fig.\[fig1\]). An intriguing feature is that the twisted structure can be distinguished in one 