More and more ONUs are connected to passive optical networks, which are prone to network congestion, information transmission delay, data packet loss, and other phenomena. Therefore, an orthogonal frequency division multiplexing passive optical network system based on information entropy characteristics is designed. The system framework structure is composed of optical line terminals (OLT), optical distribution networks (ODN), and optical network units (ONU). The system network structure is designed in a decentralized light splitting form, and the system database and data tables are designed using MySQL. Design three main functional modules of the system, namely the passive optical information transmission and reception module, the ONU load judgment module based on information entropy, and the passive optical network bandwidth allocation module. By reasonably allocating bandwidth resources, improve the transmission capacity of the passive optical network. The results show that the transmission time slot length of the passive optical network system is below 4 ms after 5 rounds of polling, and the communication transmission efficiency of the passive optical network is high, which can quickly achieve information transmission and greatly avoid delay problems.