【Objective】Soil nitrogen is an important factor in producing quality tobacco leaves. About 2/3 of the nitrogen absorbed by tobacco during its whole growth period is in the form of mineralized nitrogen. So, nitrification ratio of the nitrogen in tobacco planting soil is the key to the production of high quality tobacco. Rational application of organic manure can regulate mineralization of soil N of all forms. The aim of the study is to determine a reasonable rate for application of specialized organic manure in yellow soil in Guizhou, and to improve nitrification rate in the tobacco planting soil so as to improve quality of tobacco leaves. 【Method】In this study, samples of the yellow soil collected from Guizhou were used in an incubation test with the Stanford long-term aerobic and intermittent leaching incubation method. The test was designed to have 4 treatments, i.e. CK(0 kg•hm^-2), 1F (750 kg•hm^-2), 2F (1500 kg•hm^-2) and 3F (2250 kg•hm^-2) in terms of application rate of customized organic manure, to simulate the process of soil nitrogen mineralization. And during the incubation test, a portion of each sample in each treatment was rinsed on D0, D5, D15, D30, D45 and D60, separately, for determination of nitrification ratio. Compared with common organic manure, the specialized organic manure was higher in concentration of available nitrogen, reaching up to 41.3%.【Result】Results show that the content of mineral nitrogen, regardless of form, increased with the incubation going on during the incubation period. Mineralization was dominated by nitrate nitrogen at the early stage. After 5 days of incubation, NH₄⁺ -N turned up in dominancy. With the incubation going on, nitrate nitrogen was being mineralized. After D5, the nitrification rate of soil nitrogen in the yellow soil dropped below 10%. The proportion of nitrate nitrogen in the release of soil N was seriously lower in the late growth period. The total amount of NO₃^--N the soil could supply during the prime growing season of the plant reached only up to 66.89 mg•kg^-1, which was far from enough to meet the demand of the crop for nitrogen throughout the growing season. Once the customized organic manure was applied, soil nitrogen mineralization showed a trend of “fast first and then slow”. So soil nitrogen mineralization was high during the initial period, and then the release of mineral nitrogen reduced and levelled off at the late stage, which is in consistence with the rule of nitrogen absorption by tobacco for its growth. The application of customized organic manure increased the content of soil readily available nitrogen through mineralization significantly or even by 420.1%, the content of NO₃^--N by 276.6%,and nitrification ratio 8.1% to 50.4%. In Treatment 3F (2250 kg•hm^-2), soil nitrification rate ranged from 43.69% to 51.22%, which was the most conducive to quality of the tobacco. It was found that NO₃^--N content and total available nitrogen mineralization capacity of the organic manure increased with rising organic manure application rate. 【Conclusion】Application of the specialized organic manure at a high rate increases nitrogen supply capacity of the soil, promotes mineralization of NO₃^--N and improves nitrification rate. Especially when the application rate reaches up to 2 250 kg•hm^-2 as is in Treatment 3F, nitrification rate in the soil increases during the tobacco growing period, which is conducive to improvement of quality of the tobacco. In the tobacco growing season, application of the specialized organic manure can ensure stable release of available nitrogen and improve the nitrification rate, which is the most suitable condition for growth of tobacco plants. In conclusion, application of 2 250 kg•hm^-2 of the organic manure is the most suitable rate for tobacco cultivation in the yellow soil area of Guizhou.