Abstract: Based on flight experiment of internal discharging monitor on CRRES spacecraft,much key research was achieve on internal charging.These works establish stable base for constitution of NASA-HDBK-4002.This paper aim at internal discharging monitor that is made in laboratory and use GEANT4-RIC method simulation and experimentation to contrast discharging status of internal discharging monitor.The work validate correctness of the simulation and provide a new design method for developing space radiation effect ion monitor.