In this paper, the single event effect of N-well resistor is simulated by using the technology computer aided design (TCAD) software. The results indicate that a single heavy ion incident into the N-well resistor will make a disturbance in the output current of the device. The working mechanism of the N-well resistor and the physical mechanism introduced by the single event effect are studied. The results show that ion-induced electron-hole pairs neutralize the depletion region in the N-well substance that provides high impedance for the device, resulting in the instantaneous increase of the output current. The larger the destroyed area of the depletion region in the N-well resistor, the higher the peak value of the transient output current is. But the ion-induced disturbance can disappear with the collection of the high concentration of excess carriers in the N-well structure. However, the unique aspect ratio design of the N-well resistor makes only the carriers close to the input drift to output under the electric field. And, the drift motion of carriers takes a lot of time because of the long transport distance, which leads to low efficiency of collecting excess carriers and a long duration of ion-induced disturbance in the N-well resistor. Besides, some other factors that can affect the single event effect in the N-well resistors are also studied in this paper. The results show that the higher the LET value of ions and the farther the incident location from the input, the more serious the single event effect of N-well resistance is. In addition, properly shortening the length of the N-well resistor and increasing the input voltage of the N-well resistor can enhance its resistance to single event effect.