A field experiment was carried out with early flowering K326 plants to study the effects of different branching-after-topping treatments and various dressing rates of nitrogen on chemical components of flue-cured tobacco midribs, and determine the optimum nitrogen dressing rate. The results showed that branching at higher leaf position in maturity stage might result in lower level of chlorophyll in midribs, and much easier yellowing of tobacco leaves. While branching at lower leaf position with different nitrogen dressing level could reduce the contents of nicotine and starch in midribs of middle and upper leaves. The nitrogen dressing level of 15 kg / ha is recommented to meet the requirement of reducing production costs and improving tobacco leaf quality and safety.