Porous cordierite was synthesized by the mechano-chemical processing using fly ash. The phase evolution of cordierite was investigated as a function of processing variables such as milling time and sintering temperature. In this study, the phase transition path of cordierite from fly ash was followed by sapprine/spinel ${ o}$ mullite/spinel ${ o}{alpha}$-cordierite. Porous cordierite fabricated after 32 h of milling time and sintering at $1150^{circ}C$ showed relatively low thermal expansion coefficient ($2.5{ imes}10^{-6}/^{circ}C;(25{sim}1000^{circ}C$)) and high porosity (75%).