Optimal blending ratio of high coking Moolarben coal as a blended fuel of pulverized coal fired plant was investigated by 100 kg/h test furnace through blending with design coal, Energyman bituminous coal. The experiments of less than 20% blends at 100 kg/h furnace showed that the combustible matters of more than 99.60% at distance of 3.5 m from burner burns more completely in the boiler whereas combustion efficiency of Moolarben coal was very low due to low reactivity because it has high swelling number and pore clogging of chars. The blends of more than 40% of Moolarben coal resulted in almost 13 times the slag deposition rate on the nearest probes from burner compared to Energyman coal. The increased slagging behavior of its blends is probably due to agglomeration and deposition of unburned carbon with alkali mineral composition. It was therefore proposed that the combustion of blends of Moolarben coal with less than 20% was the most appropriate operation for the prevention of burner clogging at the pulverized coal fired boilers, and, has the excellent combustion efficiency.