A two dimensional heterogeneous model considering radial velocity profile in a radial flow reactor was established. The effect of flow maldistribution on the performance of a 3 beds radial flow ammonia converter was discussed. By computation, the results indicated that flow maldistribution has definite effect on the performance of a radial flow bed. By improving inlet temperature, decreasing inlet ammonia concentration and increasing activity coefficient, the effect of flow maldistribution could be decreased. Flow maldistribution has small effect on the performance of the 3 beds radial flow converter, and compared with the ideal flow, the yield just drops 2 percent when the degree of maldistribution reaches 70% in computation condition.