An isobaric type diesel combustor comprises an inner compressed air tube and an outer oil tube sleeved outside the inner compressed air tube, wherein two ends of the inner compressed air tube extend out of the outer oil tube; one end of the inner compressed air tube is connected with a diameter-variable inner compressed air tube, the diameter of the diameter-variable inner compressed air tube is larger than that of the inner compressed air tube, and an oil passing hole is arranged on the diameter-variable inner compressed air tube; one end of the outer oil tube is connected with a diameter-variable outer oil tube sleeved outside the diameter-variable inner compressed air tube, and the diameter of the diameter-variable outer oil tube is larger than that of the outer oil tube; sealing end covers are arranged on the end portions of the diameter-variable inner compressed air tube and the diameter-variable outer oil tube, and ejecting holes communicated with the diameter-variable inner compressed air tube are arranged on the sealing end covers. The isobaric type diesel combustor is simple in structure, easy to control due to the fact that no oil gas proportion adjusting valve is installed and capable of stably supplying compressed air to atomize diesel, and enables the diesel atomizing effect to be stable, an incinerator is stable in combustion, protective halt and flameout of the incinerator can be prevented, temperature fluctuation of the incinerator is small, and the combustor is safe and reliable to use.