<b>Data Flow Diagram DFD in Developing Online Product Monitoring System OPMS of DTI</b> The paper examined the model of data flow diagram in developing OPMS of Department of Trade and Industry. It based from waterfall model in which descriptive research was applied to the existing product monitoring of DTI. Data from existing monitoring of DTI were interpreted and created system data flow diagram DFD . The data flow diagram as applied in the analysis of software development and examined top down method that takes process the input and output of data flows. Thus, the method of developed based on the data flow diagram created will enhance the security and order of the developed online system. Data Flow Diagram, Data Aging, Security, Development, Input and Output data flows 1-7 Issue-6 Volume-2 Bryan L. Guibijar