The invention relates to a rapid-crystallization and high-toughness glass fiber reinforced PET (Polyethylene Terephthalate) composite material. The PET composite material consists of the following components in parts by weight: 100 parts of PET, 5-10 parts of reaction anti-impact modifier, 10-20 parts of crystallized modified master batch, 15-30 parts of glass fibers and 0.5-1 part of processing aid. The invention further provides a preparation method of the PET composite material. Compared with the prior art, the preparation method disclosed by the invention is technically combined with a maser-batch process technology and a reaction co-blending modification technology, so that the crystallization performance and toughness of the PET material are optimized more efficiently, and therefore, the obtained glass fiber reinforced PET composite material is excellent in mechanical performance, thermal performance and dimension stability and good in processing forming performance, and has outstanding advantages in toughness.