The fault system of the Maichen Sag in the Beibuwan Basin is very complex. In order to reveal its ge-netic mechanism, sandbox modelling technologies were applied in this paper to make a systemic analysis on the formation mechanism of the eastern fault system based on the structural analysis of 3D seismic data. The results show that the faults in the Maichen Sag can be divided into the upper and the lower fault systems. The lower fault system was formed by the NW-SE oriented regional tensile stress during the Changliu and Liushagang periods, and the upper fault system was formed by the NW-SE oriented regional tensile stress and right-lateral strike-slip stress during the Weizhou period. The lower fault system was greatly influenced by basement faults, and their di-rection, orientation and fault combination were consistent. The upper fault system was less affected by basement faults, which was mainly new faults or inherited transform faults. Fault direction was directly affected by strike-slip degree during the Weizhou period. The experimental results under the condition of weak strike-slip are con-sistent with the actual geological characteristics, and the development of secondary faults is conducive to the for-mation of structural traps, which play a guiding role in 3D seismic fine structure interpretation.%北部湾盆地迈陈凹陷断裂系统十分复杂，为了明确其成因机制，在三维地震资料构造解析的基础上，应用砂箱模拟实验，对迈陈凹陷东部断裂系统形成进行分析。结果表明，迈陈凹陷东部可划分为上、下2套断裂系统，下部断裂系统是受长流-流沙港期NW-SE向区域拉张应力形成，上部断裂系统是受涠洲期NW-SE向区域拉张及右旋走滑应力形成。并且下部断裂体系受基底先存断裂影响较大，走向、倾向、断层组合都与其保持一致；上部断裂体系受基底断层影响较小，多为新生型断层或继承改造型断层。涠洲期走滑程度的强弱直接影响断裂发育的走向，弱走滑条件下实验结果与实际地质特征吻合度高，并且发育的次级小断层有利构造圈闭的形成，对三维地震构造精细解释有指导作用。
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