The invention relates to a PBT material composition and the preparation method for secondary coating the optical fiber. The composition is to add the expanding chain agent, the elasticizer and the antioxidant into the PBT which the viscidity is the 0.8-1.4 (dl/g) to modify it into the first batch feeder by the screw machine, the PBT material with the viscidity of 1.2-1.4 (dl/g) is the second batch feeder, then to mix the two batch feeder according to the ratio of 0:10-3:7. So the production efficient of one autoclave is improved to 2t/1-2h, also it uses the PBT material with the high viscidity to proper for producing the PBT material of secondary coating the optical fiber to improve the product character greatly. |