Abstract: To select an effective intercropping ratio for flue-cured tobacco and to control tobacco black shank, field disease investigation and real-time quantitative PCR were used to study the effects of different row ratios (1:6, 1:4, 1:2 and 1:0) between tobacco to peanut on black shank control. The results showed that with the increase of peanut row, the amount of pathogen of Phytophthora nicotianae in soil and tobacco black shank disease index decreased, hence indicating that the control efficacy for tobacco black shank was promoted. The control effects were better when the ratio was 1:4 or 1:6, and no significant difference was found between them. Taking tobacco black shank control and tobacco crop yield into account, the recommended row ratio of tobacco to peanut was 1:4.