The paper examines the data flow diagram model in developing Online Product Monitoring (OPMS) for the Department of Trade and Industry (DTI). It is based on the 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 is applied in the analysis of software development and examined the top-down method that takes processes the input and output of data flows. Thus, the method of development based on the data flow diagram created will enhance the security and order of the developed online system.