Microstructure evolution can cause changes in dislocation density during hot plastic formation of metals and greatly influence the shape of flow curves. Recrystallization kinetics and average grain size were simulated by the coupled flow stress model describing dislocation development and microstructure evolution. The model for microstructure evolution considered different kinds of recrystallization in the same process rooted from nucleation and grain growth. Flow stress was calculated from the average dislocation density determined by the dislocation density model, which took into account hardening and recovery during the hot deformation process. Model parameters were defined by inverse analysis of flow curves obtained from hot compression tests and were completed through solving a nonlinear least-squares problem with constraints using optimization methods. Finally, the results obtained by the proposed model were compared with experimental results.