Due to the progressive penetration and usage of renewable sources and loads based on power electronics, medium voltage direct current (MVDC) distribution system is getting broad attention. Direct current circuit breakers (DCCBs) are of vital importance for the reliability and flexibility of power system. With features of low cost and micro-operating losses, multi-port hybrid DCCB with negative voltage source (NVS) has been proposed by the authors and might be a better choice. To further promote its industry application in MVDC system, interaction characteristics between DCCB and power system are investigated in this study. The structure of multi-port hybrid DCCB is briefly introduced. Then, considering the diversified working conditions, e.g. single fault, multiple faults and switching load current with random direction, the cooperation sequence of components in multi-port DCCB under all these working conditions is proposed, respectively. Then, based on simulation model established in PSCAD/EMTDC, transient current/voltage distribution pattern inside multi-port DCCB and its mechanism are discussed, and simulation results have verified the superiority and effectiveness of multi-port hybrid DCCB with NVS in MVDC system.