The invention discloses a low-nitrogen combustion device based on brown coal. The low-nitrogen combustion device comprises a primary air supply device, a secondary air supply device and a first channel. The primary air supply device is connected with a combustor through a first pipeline. The first pipeline is connected with an over fire air cavity through a first branch. The secondary air supply device is connected with the over fire air cavity through a second pipeline, and the second pipeline is connected with the combustor through a third pipeline. The first channel is provided with a heater and used for increasing the primary air temperature. According to the device, a heating device is additionally arranged in a primary air flue, the proportion relation of various kinds of air supply is adjusted, the combustion stability and temperature of pulverized powder particles can be effectively ensured when high-moisture brown coal is combusted, the primary air rate is increased, and the defect that a traditional low-nitrogen improvement effect is not obvious is overcome.