Alumina powder was added in a general porcelain (Backja) with clay, feldspar and quartz contents to promote the mullite ($3Al_2O_3{cdot}2SiO_2$) generation in the porcelain. Low melting materials ($B_2O_3(450^{circ}C)$, $MnO_3(940^{circ}C)$, CuO($1080^{circ}C$)) were doped at ~3 wt% to modify the sinterability of porcelain with a high alumina contents and promote the mullite generation. Green body was made by slip casting method with blended slurry and then, they were fired at $1280^{circ}C$ for 1hr by a $2^{circ}C/min$. Densifications of samples with high alumina contents (20~30 wt%) were impeded. As the doping contents of low melting materilas increased, the sinterability of samples was improved. The shrinkage rate and bulk density of samples were improved by doping with low melting materials. Mullite phase increased with increasing the low melting contents in the phase analyses. This means lots of alumina and quartz were transformed into mullite phase by low melting contents doping. In the results, high bending strength of samples with high alumina contents was accomplished by improving the densification and mullite generation in the porcelain.