A full biodegradable mulching film master batch for inhibiting weeds is prepared from the following components in parts by weight through blending: 30 to 80 parts of PBAT [Poly(butylene Adipate-co-Terephthalate)], 15 to 35 parts of carbon black, 5 to 25 parts of a herbicide and 1 to 10 parts of a carbon black dispersion treating agent. According to the full biodegradable mulching film master batchdisclosed by the invention, by utilizing an adsorption function of the carbon black, the herbicide is mixed into the carbon black, a carbon black master batch is granulated and formed through high-speed stirring and mixing and under the action of a biodegradable resin carrier, and then the carbon black is added into a degradable mulching film material in proportion so as to form a thin film through blowing; the herbicide enters internal gaps of the carbon black during a mixed treatment process and is coated by the carbon black, so that the herbicide cannot be separated out during a mulching film blowing process..