Single event effect in near space is investigated via numerical model simulations and circuit simulation of inverter with feature size 0.1μm. The numerical simulation results show that the critical charge of microelectronics device is decreased with supply voltage and the sensitive cross section is increased with the decrease of the critical charge, which leads to an increased single event upset rate in the device in near space, however single event upset rate is also decreased with the rising of the near space height. Moreover, the single event upset is observed in the inverter with SPICE circuit simulation by the pulse injection. The obtained results are helpful to performing a deeper study of the single event effect in near space and also provide a theory guide for radiation hardened.