The invention discloses a glass fiber reinforced polycarbonate composite material and a preparation method thereof. The glass fiber reinforced polycarbonate composite material is prepared from the following components in percentage by mass: 40%-76% of PC, 10%-30% of silicon resin, 3%-8% of a compatilizer, 0.4%-1% of an antioxidant, 0.6%-1% of a lubricant and 10%-20% of a glass fiber. The glass fiber reinforced polycarbonate composite material disclosed by the invention is good in mechanical property, high in mobility, excellent in chemical resistance and few in floating fibers on surface; the problems that a traditional glass fiber reinforced polycarbonate composite material is poor in mobility and serious in floating fibers when being applied to thin-wall products can be well solved; and the glass fiber reinforced polycarbonate composite material can be applied to production of ultrathin mobile phone shells which are high in rigidity, good in appearance demands and high in solvent resistance requirements.