The invention belongs to the technical field of fiber reinforced plastic forming and discloses a cotton tape winding method for a fiber reinforced plastic layer of a special-shaped structure metal shell. The method is specific to a non-rotation-body structure part composed of a rotation body and a rhombic special-shaped structure and comprises the steps that before winding, a glue film is bonded to the surface of the metal shell; cotton tape is wound on the non-rotation-body structure part through a three-axis winding machine; the cotton tape is firstly wound on the rotation body and then gradually wound on the rhombic special-shaped structure in a transition mode; the maximum rotation speed of a spindle of the winding machine is 25 r/min; and the cotton tape is pressed tightly by applying curing pressure through a vacuum bag pressing forming technology. The winding angle of the long edges of the rhombic section of the rhombic special-shaped structure is C1, the winding angle of the short edges of the rhombic section is C2, the winding angle of the remaining parts is C, and C is greater than or equal to C2 but small than C1; and the wound cotton tape width B is equal to A*SinC, the winding feed amount D is equal to E/SinC, A is the thickness of a heat shield layer, and E is the thickness of the cotton tape. According to the cotton tape winding method, special-shaped fiber reinforced plastic layer forming control is achieved through effective parameter design and technique process control.