JUNO is a multi-purpose neutrino experiment designed to determine the neutrino mass hierarchy and precisely measure oscillation parameters. The offline data processing of JUNO is based on the newly designed and developed SNiPER framework which provides flexible event management buffer, efficient event execution controlling, user-friendly interfaces and so on. The event data model of JUNO is based on the ROOT TObject. A new type of smart pointer, SmartRef, is designed to meet the special multi-event correlation requirements of neutrino experiments. SmartRef uses the Universally Unique Identifier to handle the references of event data objects, both in memory and in ROOT files. The Input/Output system supports the lazy-loading of event objects when reading data from ROOT files. So far, JUNO offline data processing software has been successfully used for the optimization of detector performance as well as study of reconstruction and physics performance.