The invention discloses a fertilizing method for tobacco in a manner of drip irrigation under a plastic film. A drip irrigation system is used for sending a water fertilizer mixed solution required by each stage of the tobacco growth to a tobacco root zone soil; the water fertilizer mixed solution is one or more of compound fertilizer aqueous solution special for tobacco, phosphate fertilizer aqueous solution, potassium nitrate aqueous solution and potassium sulfate aqueous solution; and the compound fertilizer special for tobacco and the phosphate fertilizer are applied as base fertilizers in a transplanting process, the dosage of the compound fertilizer special for tobacco is reduced and the application time of the potassium sulfate is delayed in stages. The invention positively responds to the double reduction plan established by the Ministry of Agriculture, the dosage of nitrogen and phosphor is greatly reduced and the agricultural non-point source pollution is reduced. Compared with the conventional fertilizing, the invention has the advantages that the drip irrigation under the plastic film is adopted for fertilizing, the dosage of the potash fertilizer is not changed, the total dosage of the nitrogen and phosphor fertilizer is respectively reduced by 15kg/hm<2> and 18kg/hm<2>, and meanwhile, the obvious output reduction is not caused and the output value is basically not changed. Various chemical components in the tobacco leaves are close to harmonious and balanced state and are approximate to the suitable content scope of high-quality tobacco leaves.