This paper proposes a method that employs successive interference cancellation (SIC) to further enhance the capacity of uniform circular array (UCA)-based orbital angular momentum (OAM)-MIMO systems. The main feature of the proposed method is to stabilize the performance of UCA-based OAM-MIMO systems by conducting SIC based on the results of parallel interference cancellation (PIC), which exploits the additional full space diversity benefit. The development of the proposed approach is motivated by the feature that large differences in the received power of different UCAs are advantageous to SIC. Moreover, the impact of the misalignment of the beam axis on the effectiveness of the proposed method is also investigated by considering a more realistic scenario. Our numerical results show that the effectiveness of the proposed method increases with increasing number of UCAs, and its advantage is retained within a certain amount of the misalignment of the beam axis.