The invention discloses a method for manufacturing an external coating layer of an optical fiber preform rod through a sleeve method, belongs to an optical fiber manufacturing technology and aims to overcome the defects of sleeve waste and the like in the manufacturing of an external coating layer of an optical fiber preform rod through a sleeve method in the prior art. In the invention, a core rod is welded onto an auxiliary glass rod, an external diameter enlarged part is arranged at the welding position, and the whole core rod is concentrically inserted into a sleeve, thus forming an annular space between the external surface of the core rod and the internal surface of the sleeve; the circumference of the sleeve is provided with at least three recess parts for fixing the core rod; a blowtorch is used to heat the external diameter enlarged part which seals the sleeve and the core rod, and negative pressure is applied to the annular space; and the blowtorch is moved to heat the sleeve and the core rod, so that the sleeve can collapse onto the core rod to form a solid optical fiber preform rod. According to the invention, the sleeve utilization rate is high; the existing improved chemical vapor deposition equipment can be fully utilized, no additional equipment investment is required, the production cost can be lowered, and the production time can be saved; and the optical fiber preform rod manufactured by the method has favorable physical dimension.