After coal injection system of 2200 m3 BF were built in Anyang, some problems affecting the system works were found , such as the injection ability is low and the injecetion quantity exists high deviation. However, remarkable effect was achieved after the system were rebuilt. The injection capacity is improved from 20 t per hour to more than 45t per hour, and the injection deviation is reduced from 1ton per hour to 300kg per hour. The measures were used in coal injection system of another 2800 m3 BF and got a satisfactory effect.