The investigation and modelling of the 4H–SiC merged PiN/Schottky (MPS) diode are presented for superior surge current capability design. A bipolar current transmission (BCT) model is proposed for investigating the current transport mechanism of MPS diodes under bipolar operation. The knee voltage (Vturn) defining the conversion from unipolar to bipolar operation is precisely modelled for controlling surge current. According to the proposed model, the method of designing a SiC MPS diode with high robustness against surge current is discussed and concluded primarily, which has great significance for improving the reliability of SiC MPS diodes. Meanwhile, we propose a new hybrid stripe cell design according model calculation and simulation for enhancing the surge current capability of the diode while maintaining high forward current capability. The proposed model and design method are verified by experimental results. And the proposed hybrid stripe cell design has superior surge current robustness while it almost avoids the forward current degradation in experiment.