Metallic-monolith catalyst support with self-growing porous anodic alumina (PAA) film was prepared by anodizing Al plate. The effect of hydrothermal treatment (HTT) on the crystalline state and textural properties of PAA film was investigated by XRD

BET

SEM and TG. The HTT treatment above 50℃ and the subsequent calcination above 300℃ could convert the amorphous skeleton alumina into γ-alumina and increase the specific surface area (

S

BET

). However

SEM images showed the HTT modification was a non-uniform process along the thickness of PAA film. The promotion effect of HTT on

S

BET

was non-linear

and the slope of

S

BET

gradually decreased with the HTT temperature or time increased. The limited HTT effect should be attributed to a changed pore structure caused by an unfavorable pore sealing limitation. Pore widening treatment (PWT) before HTT could break the pore sealing limitation

because of the reduced internal diffusion resistance of hydrothermal reaction. The synergistic combination of PWT and HTT developed a PAA support with a large

S

BET

comparable to commercial γ-alumina. In the catalytic

combustion of toluene

the Pt-based catalyst prepared by using the PWT and HTT comodified PAA support gave higher Pt dispersion and more favorable catalytic activity than that treated by HTT alone. The presence of a bimodal pore structure was suggested to be a decisive reason.