The invention discloses a coil production method and a production line thereof. The production line comprises a heating furnace, a rough rolling unit, a medium rolling unit, a pre-finish rolling unit, a finish rolling unit, a reducing and sizing unit, a spinning machine, an air-cooling line, a reel collecting station and other devices. A blank is subjected to the first step of heating, the second step of rough rolling and medium rolling, the third step of pre-finish rolling and finish rolling, the fourth step of reducing and sizing, the fifth step of spinning, the sixth step of fast cooling after spinning, the seventh step of air-cooling line controlled cooling and the eighth step of reel collecting and packaging in sequence on the above devices. Controlled rolling in a critical austenite area is achieved by accurately controlling the rolling temperature, the low-temperature phase change is achieved, a rolled piece directly enters the spinning machine without being subjected to water cooling after reducing and sizing are conducted, the phenomenon of water blocking caused during small-specification water passing is effectively avoided, the production fault rate is reduced, the distance between the reducing and sizing unit and the spinning machine is shortened, and the length of the cooling line is reduced; and due to the combination of two sections of water cooling and air cooling after spinning, the cooling efficiency is improved, transformation of a control structure is achieved, investment is reduced, and the market competitiveness is improved.