Ｎｅｅｄｌｅ法是一种先进的膜系设计方法，它克服了传统优化方法容易陷入局部极值的缺点。通过在膜系中插入薄层，使得评价函数降低，优化设计可以从任意给定的一层膜开始。文中给出了其数学模型及详细的推导。 Needle method is an advanced membrane design method, which overcomes the shortcomings of the traditional optimization methods easy to fall into the local extremum. By inserting a thin layer into the film system, the evaluation function is reduced and the optimized design can start with any given layer of film. The paper gives the mathematical model and detailed derivation.