Processes for producing carbon fibre, the filament thereof and pre-oxidized fibre are provided. In one embodiment, the gel spinning of polyacrylonitrile filament is achieved by using small-molecule gelling agent, and the carbon fibre obtained thereby is increased by 15% to 40% in tensile strength and by 20% to 35% in toughness. In another embodiment, the melt spinning process of polyacrylonitrile is conducted by using imidazole type ion liquid as plasticizer, the process reduces environment pollution, is suitable for industrial production and the fibre produced thereby is improved in its strength. In yet another embodiment, polyacrylonitrile pre-oxidized fibre is produced by melt spinning, so low cost and controllable pre-oxidization of polyacrylonitrile can be achieved. In a further embodiment, high strength carbon fibre is manufactured by using polymer thickening agent. In another further embodiment, low cost and controllable pre-oxidization of polyacrylonitrile is achieved by conducting pre-oxidization before spinning, minimizing skin-core structure, so as to produce high performance carbon fibre, and reduce the production cost of carbon fibre greatly.