function getFormJson(frm) { //frm：form表单的id
    var o = {}; 
    var a = $("#"+frm).serializeArray(); 
    $.each(a, function() { 
      if (o[this.name] !== undefined) { 
        if (!o[this.name].push) { 
          o[this.name] = [ o[this.name] ]; 
        } 
        o[this.name].push(this.value || ''); 
      } else { 
        o[this.name] = this.value || ''; 
      } 
    }); 
    return o; 
  }

$.ajax({
  type: 'post',
  url: 'your url',
  data: getFormJson(frm),
  success: function(data) {
    // your code
  }
});