The invention belongs to the technical field of agricultural production, in particular to a method for picking cotton in a mountainous area. A cotton picking device used in the method comprises a machine shell, a driving cylinder, a driven cylinder, a steel belt, a steel needle, a battery pack, a solar panel, a handle, a control switch, a cotton collecting box, a filter sheet, a fan, a cotton picking roller and cotton picking blades. A set of the cotton picking blades is fixedly connected to the cylindrical surface of the cotton picking roller; a set of first rectangular grooves is formed in the cotton picking blades, and the cotton picking blades are used for removing cotton on the steel needle. The cotton picking roller is arranged on the right side of the driving cylinder, a set of thecotton picking blades are fixedly connected with the cylinder surface of the cotton picking roller, and the cotton picking roller is rotated, so that the cotton picking blades are driven to remove thecotton on the steel needle, the situations that the steel needle brings the cotton out of the machine shell and causes scattering of the cotton and unnecessary trouble, and the picking efficiency isinfluenced are prevented, and the cotton without cotton leaves is sucked by the fan on the right to be brought into the cotton collecting box.