Abstract: With optical microscope,micro-hardometer, scanning electron microscope（SEM）,EPMA and X-ray diffraction method,investigations on the microhardness and the phase composition characteristics of the Fe-Al alloyed layer of the GL aluminized（induction slurry process）steel tube were made.The result shows that the microhardness of the said aluminized layer ranges inward from 600 HM to 320 HM,while the layer itself is composed by α-Fe（Al） solid solution, Fe₃Al and FeAl,and that no high Al containing brittle phases like those of FeAl₂, Fe₂Al₅, and FeAl₃ are found,which means better deformation resistance and weldability of the aluminized steel.