This report aimed at investigation on the application of atomic force microscope (AFM) in research on interaction between cells and extracellular matrix, and function of extracellular matrix. Distribution and array of fibronectin fibrils surrounding human breast carcinoma MCF-7-R cells were observed by atomic force microscope, and comparison of AFM with other traditional techniques was performed. Whole and local AFM morphological images of several human breast carcinoma MCF-7-R cells and fibronectin fibrils around cells were obtained by AFM. Distribution and array of fibronectin fibrils were found to be very regular, and the regulated array coordinated with functions of fibronectin fibrils very well. Owing to advantages of simple sample preparation and very high resolution, AFM is an ideal tool to in situ observation of extracellular matrix.