The computation method of the interaction force between adjacent dislocation segments and the discretization method of the dislocation line in the 3D model of discrete dislocation dynamics were improved in order to simulate the evolution of Frank-Read (FR) dislocation source on the meso-scale. The simulation results show that the improved model can more accurately simulate the critical shear stresses and dislocation configurations of the FR dislocation sources with different initial lengths. Moreover, the smaller dislocation loop is formed by FR dislocation source when larger stress loaded, and approaches the dislocation loop formed without considering the interactions among the dislocation segments. Under the same loaded stress, the larger loop is formed with increasing the Peierls stress. However, the drag coefficient only affects the formation time of the loop, but can not affect the loop size. This kind of nonlinear evolution of dislocation is caused by the interactions among the dislocation segments.