In order to reduce the cracking risk of transition fillet of the groove bottom of deep groove forging mold, and provide guidance for the structural design of forging mold, a mold was designed to study the influences of structural parameters (transition fillet radius of groove bottom R, single side height of bridge for flash groove h, inlet fillet radius r, draft angle α) on mold stress (maximum principal stress of mold). Then, four sets of simulation experiments were designed by using the single factor variable method, and a total of twenty-four finite element simulation experiments were carried out. Furthermore, the simulation correctness was verified by comparing the simulation results of forming load with the prediction results of existing studies. The simulation results indicate that σmax (maximum mold stress value) decreases with the increasing of R, and the two show a good linear relationship, that is, R increases by 1 mm, and σmax decreases by about 40 MPa. The overall stress level of mold decreases rapidly with the increasing of h, but the degree of reduction decreases gradually. r has little effect on the mold stress when r changes from 1 mm to 7 mm, and the influence mechanism of α on the mold stress is more complicated. In general, increasing α induces a slight increase in the mold stress.