During the inertia friction welding (IFW) process of superalloy GH4169, the main mechanism for microstructural evolution is dynamic recrystallization (DRX). In order to investigate the microstructural evolution during the process, a finite element (FE) model coupled with the DRX model of the alloy was developed on the platform of MSC.Marc. Equivalent strain was introduced into the DRX model to improve the computational precision. As a result, the IFW process with microstructural evolution was simulated. Simulated results reveal that DRX region is very small. Fully recrystallized region and fine grains appear near the weld line. Dynamically recrystallized fraction (DRXF) decreases and grain size increases with the increase of the distance from the weld line. Predicted results of microstructural distribution agree well with experimental ones.