In order to establish approximate attachment function, esp, when there are many factors to determine, a simple, practical and effective method is presented: occurence statistic iterative method for determing grade attachment. 给出了在实际应用中为建立近似的隶属函数,特别是对于需要确定的因素集较多的时候,确定隶属度的一种简单可行且有效的方法&集值统计迭代法。