The invention relates to the technical field of high polymer materials, in particular to a transparent flame-retardant antistatic PMMA composite material and a preparation method thereof. The transparent flame-retardant antistatic PMMA composite material comprises the following components in parts by weight: 70.00-99.00 parts of methyl methacrylate, 0.03 to 0.20 part of an initiator, and 1.00 to 30.00 parts of a flame-retardant antistatic agent, wherein the flame-retardant antistatic agent is prepared from first monomer, a dehydration catalyst and second monomer through esterification reaction, the first monomer contains a plurality of phosphonic acid or phosphorous acid groups, and the second monomer has both a hydroxyl group and a double bond at the same time. The composite material enables PMMA to achieve the flame retardant effect and the antistatic effect, has the flame retardant grade of UL-94V-0, the surface resistance of 1,012 omega or less, has the obvious flame retardant andantistatic effect and has permanent flame retardant and antistatic properties without affecting the transparency of PMMA.