By using the KKSO multiphase field model, the fixedvelocity growth and velocitychanging growth of directional solidification for eutectic CBr4C2Cl6 alloys are simulated in three dimensions to reproduce the morphology evolution and selection. The diagram of the eutectic morphology selection is further established. The changes of the average interface velocity and the average interface undercooling during velocitychanging growth are also studied. The simulation results show that the eutectic morphology selections both before and after velocity change are the same as the morphology selection in the case of fixed pulling velocity. For all of the eutectic morphology selections, changes of the average interface velocity and the average interface undercooling show the hysteresis effect. It's also found that the relationship between the average interface velocity and the average interface undercooling is in good agreement with the theoretical prediction.