In the vacuum film coating field, the co-sputtering method by two or more targets has been widely used for coating the composite film consisted of a variety of component elements. In this paper, a typical co-sputtering system is studied which composes the twin round planar magnetron sputtering targets settled symmetrically and slantways towards a single flat substrate with self-rotation. A model is set up to describe the non-dimensional relationship between the film thickness and the structural parameters of co-sputtering system, such as distance of the substrate-to-target , symmetrical eccentricity , translation length and obliquity angle of target . On the assumption that the sputtered particles are emitted in the direction of cosine distribution and fly straightly without collision scattering, the depositing rate distribution, film thickness distribution, the utilization ratio of the target sputtering material, and the fluctuant ratio of the components from two targets are calculated. Some of simulating examples are given by use of Matlab software.