在连续变量复合形算法的基础上 ,采用平均值舍入法获取离散点 ,改进了复合形迭代过程和停机准则 ,使之成为一种能直接求解离散变量优化解 .将该方法应用于同济大学开发的钢结构杆系CAD软件——— 3D3S ,建立了门式刚架结构离散变量优化的数学模型 ,实现了门式刚架结构的优化 ,取得了较好的效果 Based on the continuous variable compound algorithm, the average value rounding method is used to obtain the discrete points, and the complex iterative process and stopping criterion are improved, which makes it an optimal solution that can directly solve the discrete variables. This method is applied to Tongji University Development of steel structure rod CAD software --- 3D3S, the establishment of a portal frame structure discrete variable optimization mathematical model to achieve the optimization of the portal frame structure and achieved good results