Abstract: Precise measurement of foam shape after assembling is necessary. Optical interferometry can obtain cross-sectional structure images of sample with 1-2 mm depth below surface, therefore the shape change is observed. In this paper, optical interferometry is applied to quality demonstration of foam in hohlraum. An optical interferometer based on low coherent light source is established and inner structure images of assembled foam are obtained with a spatial resolution better than 10 m. Superficial and inner structure changes of the foam after extraction are detected, which helps to demonstrate the quality of the assembled foam.