The invention relates to PBT (polybutylene terephthalate) composite and a preparation method thereof. The preparation method includes: weighing 60-80 parts of PBT, 50-60 parts of glass fiber, 0.1-0.3part of SEBS-g-MAH (styrene-ethylene-butyl-styrene grafted maleic anhydride), 2-6 parts of gloss modifying master batch, 0.1-0.3 part of Chimassob 2020 and 0.1-0.5 part of an antioxidant; mixing to obtain a mixture; granulating the mixture by extrusion to obtain the PBT composite. The principle of gloss modifying master batch is employed, silicone helps improve dispersibility of glass fibers in PBT matrix, interfacial compatibility of the glass fibers with the PBT matrix is improved, and apparent quality is improved; melt index improver CBT-100 can be added to improve melt index of the PBT matrix and reduce flow resistance of molten PBT, and apparent quality is improved accordingly.