The invention relates to a biodegradable polycarbonate butylene terephthalate composite material and a preparation method of the biodegradable polycarbonate butylene terephthalate composite material. The biodegradable polycarbonate butylene terephthalate composite material is characterized in that the material comprises the following components in part by weight: 30 to 70 parts of aliphatic polycarbonate butylene terephthalate, 10 to 40 parts of other biodegradable materials, 1.0 to 10 parts of filler, 0.5 to 1.5 parts of rare earth composite nucleating agent, 0.5 to 1.5 parts of dispersant, 4.0 to 15 parts of plasticizer, 1.5 to 4 parts of heat resistance stabilizer, 0.05 to 1.5 parts of antioxidant, 0.5 to 1.0 part of lubricant, 0.1 to 1.0 part of anti-block agent and 0.05 to 0.5 part of biodegradation accelerator. The composite material has high melt strength, good film forming ability, high tensile strength, high tearing strength and good light-conversion effect.