Information technology rapidly increases by time and things are becoming more challenging nowadays, one of which is by using an e-commerce platform that makes perishable products, including fishery products become one of the commodities that attract market attention. However, due to the long and complex supply chain of fishery products, there are many problems faced by suppliers and customers of this perishable product. The discussion using the process-chain network method in this study aims to reduce supply chain complexity through digital platforms. An online digital auction system can give customers direct access to the upstream of the supply chain and can expand the market. The method used business process modelling using the PCN (Process Chain Network) concept through literature study to obtain a business model that is easily understood by all parties and data collection through interviews. The data that has been obtained is analysed by procedures and is described in the form of a diagram. The result is obtained an online fish auction system model in the form of a business process. Thus, this analysis is important for further research in designing Standard Operating Procedures (SOP) of online fish auctions to help establish a sustainable online fish auction.