The invention belongs to the technical field of high polymer material modification and provides a degradable high-flowability PC/PLA alloy material and a preparation method thereof. The degradable high-flowability PC/PLA alloy material is prepared from the following raw materials in percentage by weight: 45-80% of polycarbonate, 5-35% of polylactic acid, 2-10% of compatilizer PETG-G-PLA, 3-10% of a flexibilizer and 0.2-1% of other auxiliaries. After the raw materials are weighed in the percentage by weight, all the raw materials are mixed evenly, melt-extruded by use of a screw extruder and pelletized, and therefore, the degradable high-flowability PC/PLA alloy material can be obtained. The preparation method of the degradable high-flowability PC/PLA alloy material is simple in process and low in cost; the obtained degradable high-flowability PC/PLA alloy material has the characteristics of high flowability, high toughness, formability and high notch impact resistance; in addition, due to the addition of PLA, the alloy material has biodegradability, is more friendly to the environment and conforms to the development direction of materials at present.