The phase reconstruction image of digital holographic microscopy is presented to measure the refractive index of biological film.The angular spectrum method is employed to reconstruct the phase image.The quantitative relationship between the thickness of the film,the refractive index of the film and the refractive index of the liquid among the film is determined from the phase image. The thickness of the film and the refractive index of the liquid can be measured easily using wedge interference and Abbe ref...