In this paper, we propose a low complexity multipleinputmultiple-output (MIMO) detection algorithm with adaptiveinterference mitigation in downlink multiuser MIMO (DL MUMIMO)systems with quantization error of the channel state information(CSI) feedback. In DL MU-MIMO systems using theimperfect precoding matrix caused by quantization error of theCSI feedback, the station receives the desired signal as well as theresidual interference signal. Therefore, a complexMIMO detectionalgorithm with interference mitigation is required for mitigatingthe residual interference. To reduce the computational complexity,we propose a MIMO detection algorithm with adaptive interferencemitigation. The proposed algorithm adaptively mitigates theresidual interference by using the maximum likelihood detection(MLD) error criterion (MEC). We derive a theoretical MEC byusing the MLD error condition and a practical MEC by approximatingthe theoretical MEC. In conclusion, the proposed algorithmadaptively performs interference mitigation when satisfyingthe practical MEC. Simulation results show that the proposed algorithmreduces the computational complexity and has the sameperformance, compared to the generalized sphere decoder, whichalways performs interference mitigation.