It is very important that the stochastic characteristics of the absorbed energy affect the energy deposit and its radiobiological effect of ionization radiation at cell or cell cluster scale. This work built the specific code for microdosimetric quantities based on Geant4 toolkit, and studied the α-emitter ,211,A,t ,microdosimetric characteristics of a simple cell model and a virtual cell model. The feature of the single event specific energy and the survival fraction for different cell dimensions was investigated. A virtual digital cell model was implemented and its microdosimetric characteristics were studied. The influence of different materials and irregular configuration on the microdosimetric quantities was analyzed by comparing with those of the simple cell model. A Geant4 utility code for voxel-based single cell models was built for the microdosimetric research of single cell model, which is also easy to extend to the voxel-based tissue model.