采用二步阳极氧化法在草酸溶液中制备了多孔阳极氧化铝(PAA)薄膜。借助于扫描电子显微镜(SEM)分析了多孔阳极氧化铝薄膜的微观形貌。结果发现，在其表面孔径为30～40nm的六边形孔洞分布均匀，且垂直于表面平行生长。依据PAA透射光谱的实验数据，采用极值包络线算法计算出了PAA薄膜的复折射率以及光学能隙等光学常数。通过分析吸收系数与入射光子能量之间的关系发现，PAA薄膜具有直接带隙半导体的电子结构特征，而且由理论计算得到的PAA的带隙能与其光致发光谱的峰位能是一致的。

The highly ordered porous anodic alumina films are fabricated by two-step anodizing process in oxalic acid solution. The morphology of the PAA film is investigated by scanning electron microscopy (SEM),the highly ordered hexagonal pores grown in PAA with diameters of 30～40nm and thickness of hundreads of nanometers pack with each other closely. The structural and optical parameters such as complex refractive index and optical band gap of PAA film are calculated based on the envelope curves of the transmission spectrum. Through analyzing the function relation between the absorption coefficient of PAA film and the photon energy of incident light,the characteristic of the electronic structure of PAA film is proved to be that of a direct-band-gap semiconductor,and the calculated bandgaps are agree well with the PL peak energy given by experiments.