The invention discloses a full biodegradable plastic starch master batch, a preparation method and application thereof. The plastic starch master batch comprises the following compositions in portion by weight: 60 to 75 portions of starch, 20 to 30 portions of vectors, 1 to 5 portions of compatilizer, 1 to 5 portions of lubricant, 1 to 5 portions of modifier and 1 to 5 portions of degradation accelerant. The plastic master batch takes the starch as a bioactive substance which is added with light, oxygen and the thermal degradation accelerant, and has the characteristic of multi-degradation under the action of the light, the oxygen, heat and microorganisms. The degradation process of the full biodegradable plastic starch master batch is as follows: after the induction period (controllable) is over, a product is degraded into chips and powder, assimilated with the environment finally, and is continuously degraded under certain environmental condition (aerobic), and CO2 and water are finally generated and can not cause secondary pollution when entering into soil, wherein the degradation period can be adjusted and controlled as required by change of the addition of a composite degradation regulator and the bioactive substance. The full biodegradable plastic starch master batch also has the advantages of simple preparation technology, low production cost and so on.