The present invention provides an insulation film, comprising a film upper layer (101) and a film lower layer (103), wherein both of the film upper layer (101) and film lower layer (103) are made of a PP material, the PP material contains a flame retardant to meet the flame retardance thereof; a film intermediate layer (102) located between the film upper layer (101) and the film lower layer (103), the film intermediate layer (102) is made of a PP or PE material, the PP or PE material does not contain a flame retardant or contains a small amount of flame retardant; an upper surface of the film intermediate layer (102) is bound together with a lower surface of the film upper layer (101), a lower surface of the film intermediate layer (102) is bound together with an upper surface of the film lower layer (103).