A low complexity digital IQ (in-phase and quadrature) imbalance self-calibration technique in Frequency Division Duplexing (FDD) transceiver is proposed in this paper. The RX (receiver) and TX (transmitter) IQ imbalance are compensated by a digital post-correction and pre-distortion, respectively, and the correction and distortion parameters can be accurately acquired in calibration mode while the transceiver starts up. The proposed digital self-calibration scheme has been implemented to a FDD transceiver in 0.13 mu m CMOS process. The measurement shows that with the proposed calibration, 60dB image suppression is achieved in both RX and TX. This ensures a 2.12% and 2.3% EVM of 64QAM in RX and TX, respectively, comparing to 4.67% and 5.16% without the calibration.