Abstract: The combustion characteristics of swirl burners with precombustion chamber are closely related to the operating conditions and parameters, which directly affect the coal burnout and pollutant emission. It has always been the focus of industrial boiler system research and development. In order to explore the combustion characteristics and reasonable operating parameters of pre-combustion chamber swirl burner under low load operation, the pre-combustion chamber was monitored by high temperature thermocouple, flue gas analyzer and high-speed camera. The temperature distribution, component concentration distribution and flame shape outside the pre-combustion chamber were measured by high-temperature thermocouple, flue gas analyzer and high-speed camera on the basis of 14 MW pulverized coal combustion test-bed in this paper. The combustion process of pulverized coal in and outside the precombustion chamber was analyzed, and the inner and outer secondary air mass flow ratios was optimized. The test results showed that the pre-chamber swirl burner can achieve stable combustion of pulverized coal under low load operation. Meanwhile, the high-temperature anaerobic strong reducing atmosphere area in the center and the low-temperature air layer on the side wall were formed in the precombustion chamber, and the "fire in air and pulverized coal in fire" combustion state was appeared along the radial direction, which was conducive to restrain NOx generation at the initial stage of combustion and keep long-term stable low operating load. The stable turbulent diffusion flame was formed outside precombustion chamber. The exchange is conducive to the subsequent combustion of the pulverized coal in the furnace, and the outlet of the pre-combustion chamber can avoid high temperature corrosion. At the same time, the maximum radius of the oxygen-free area under the 1∶2 case is R=171 mm, which has little difference with others, while the average temperature peak value is 1 122 ℃, and the average peak value of CO concentration in strong reducing atmosphere is 13.713%, and it is obviously better than other working conditions. The flame length in the flame stroke is 4 473 mm in the flame stroke, and it is better than others, which is conducive to further reducing NOx emissions and improving pulverized coal burnout. It can be used as the optimal operating condition of precombustion chamber swirl burner under the operating conditions of 46% load, excess air ratio of 1.63 and inter secondary air swirl number of 1.6.