The invention discloses a nylon 6 melt spinning method and device under an external field condition. The nylon 6 melt spinning device comprises a fusing heating device, a containing device, a feeding device, a spinning nozzle, a fiber collecting plate and an adjustable pulsed magnet field device. The nylon 6 melt spinning device is characterized in that nylon 6 slices are heated and fused by the heating device in the containing device, subjected to pulsed magnet field processing by a certain time, pushed to the spinning nozzle through the feeding device, sprayed out and received at the fiber collecting plate; the adjustable pulsed magnet field device is composed of a pulsed magnet field generator and a cooling circulating water device; the strength and frequency of the pulsed magnet field generator are controllable within a certain range. The pulsed magnet field with the adjustable strength and frequency is applied in a traditional nylon 6 melt spinning process, a nylon 6 melt is subjected to action of the pulsed magnet field in the spinning process, the nylon 6 segmental motion activity is improved, the mobility of the melt is improved, and the diameter of the manufactured fiber is reduced, and the tensile strength is improved.