因为您发送selectQualification的值是 并且控制器期望的值是qualification。

所以要么改变

public void AcceptPersonalInfo(string name,string fatherName,string qualification) 
{}

至

public void AcceptPersonalInfo(string name,string fatherName,string selectQualification) 
{}

或改变

data: { name: $("#name").val(), fatherName: $("#fatherName").val(), selectQualification: $("#selectQualification").val() },

至

data: { name: $("#name").val(), fatherName: $("#fatherName").val(), qualification: $("#selectQualification").val() },

您可以使用BindAttribute.Prefix属性。

例如。：

public void AcceptPersonalInfo(string name,string fatherName,
                   [Bind(Prefix = "selectQualification")] string qualification){}