In order to improve the mechanical properties and the high temperature oxidation resistance, aluminizing was carried out at a temperature range between $850^{circ}C$ and $1050^{circ}C$. The pack cementation process was used to produce uniform layer. After each treatment, the microhardness and the characteristics of high temperature oxidation were tested to evaluate the properties of the aluminide layer. The aluminide layer consisted of FeAl above $1000^{circ}C$, and $Fe_2Al_5$ below $900^{circ}C$, and the mixed phase of FeAl and $Fe_2Al_5$ between 90$0^{circ}C$ and $1000^{circ}C$ in case of the mixture powder consisted of 5%Al+5%$NH_4Cl+90%AL_2O_3$. The microhardness of $Fe_2Al_5$ was obtained much as the twice as that of FeAl. As the aluminizing temperature and time increased, the thickness of aluminide increased. After aluminizing, the high temperature oxidation resistance was remarkably improved. The high temperature oxidation resistance of FeAl was superior to the resistance of high temperature oxidation of $Fe_2Al_5$.