Formation characteristics, aperture configuration and dynamic change of gas hole in the early stages of foamed aluminum were investigated based on preparation of foamed aluminum by a new powder metallurgy method with immersing preformer and heating up rapidly. The results show that foaming process is characterized by micro-propagation to macro-propagation to collapse. The formation mechanism of micro-propagation of crack-gas-hole depends on the stress from H₂ decomposed from TiH₂, characterized by transverse crack in propagation direction and distributed within solid phase. Macro-propagation is attributed to the crack propagation and growth resulting from continuous decomposition of TiH₂. The new method can reduce the heating time from 10 min to 30¹50 s, which effectively increase the dynamic mechanism of homogeneous foaming and improve the utilization ratio of TiH₂.