Aiming at the problem of module partition in the process of system modularization design, this paper proposes to analyse date flow graph, and erects abstract date flow graph, and then formalizes the definitions and module division rules of abstract date flow graph. For the telemetry system of missile-borne question, abstract date flow and fuzzy clustering are used to divide module; then, calculates the total coupling degree among the modules and obtains a unified module division scheme; finally, the best scheme is obtained through the analysis of the system. The module division scheme obtained by using this method can guide the construction of missile-borne telemetry system, the stability and data interaction efficiency of the system are guaranteed reliably.