In this study, we attempted to recycle the fly ash as a mullite whisker with addition of $Al_{2}O_{3}$ to obtain the high yield of mullite whisker. During the reaction process, mullite whisker was formed with the reaction of amorphous $alpha$-Cristobalite and Anorthite above $1350^{circ}C$. With increasing the heat treatment temperature and time, the mean length and aspect ratio of mullite whiskers was gradually increased.