The present disclosure discloses a high-temperature resistant and small-diameter optical cable and a preparation method thereof. The high-temperature resistant and small-diameter optical cable is prepared by using acrylate as a coating material, using PHB/PET liquid crystal copolyester as an outer protective layer material and using an extrusion process. Compared to traditional optical cables, the novel optical cable has advantages in small diameter, low loss attenuation, good microbending property, excellent mechanical property, long one-time finished length (10 km˜26 km), long storage time, simple preparation process and wide operating temperature range.