The invention discloses a composite roll separating, finishing and rewinding device. The device comprises a roll feeding trolley, an unwinding device, a first straight head device, a clamping deliveryand guiding device, a cross-cut shear, a longitudinal shearing unit, a pneumatic separating unit, a guiding roller, a double-layer clamping delivery unit, a loop, a first tensioning unit, a first roller front clamping delivery roller, a middle winding machine, a gathering steering unit, a second straight head unit, a welding machine, an accurate correcting machine, a rough grinder, a purging unit, a fine grinder, a cleaning and drying unit, a second tensioning unit, a weld joint shear, a second roll front clamping delivery roller, a winding machine, a film applicator and a roll discharging trolley which are connected in sequence along a production line, and further comprises a transition roller channel which is disposed below the first tensioning unit, the first roller front clamping delivery roller and the middle winding machine. The invention further discloses a composite roll separating, finishing and rewinding method implemented by adopting the device. By means of the composite roll separating, finishing and rewinding device and method, separating, finishing, surface treatment and winding of a composite roll can be achieved, and the production efficiency can be improved.