With the increasing tasks of load down operation of the power station units in China, the capacity of the boiler's low-load stable burning is more necessary. This paper proposes a new type automatic adjustable pulverized coal distributor (AAPCD) and mainly introduces the stable burning principle of this distributor and it's application in the direct-fired system in boilers with fan mills. The dependence of the characters of the automatic adjustable pulverized coal distributor on the air and coal powder flows by means of a lot of commercial tests. The results show: being applied in domestic lignite boiler of 670 t/h, this AAPCD can adjust the distribution of the air and coal powder when the boiler is running; achieve effective control of distribution of them, increasing the capacity of the boiler's low-load stable burning without oil which usually used in China while the boiler works in a low-load condition from 70% down to 45%, so we can lower the load greatly. Because the combustion of the fuel is divided into two parts-over dense combustion and over sparse combustion in boiler, the emission of NOx is less than 350ppm, the unburned carbon loss is decreased by 1.958%, So it effectively increases the thermal efficiency and improves the capacity of low-load operation.