The invention provides a fiber, fiber master batch and manufacturing method thereof. The manufacturing method includes the following steps: powder refining treatment and mixing are performed on polyetherimide powder, polyester powder and a fire retardant to form a fiber master batch material, wherein the fire retardant is utilized to perform modification treatment on the polyester powder. Then, powder scattering treatment is performed on the fiber master batch material. Afterwards, a mixing manufacturing process is performed on the fiber master batch which is subjected to the powder scattering treatment, thereby forming a fiber master batch. Thus, the fiber provided by the invention has a good flame-retardant effect and does not cause a drop melting phenomenon, and has dyeability.