在闪吧看到的
给动态文本加个滤镜，alpha就可以变了，呵呵。试了下_rotation，不行

import flash.filters.BlurFilter;
var txt_blur:BlurFilter = new BlurFilter(0, 0, 0);
var speed:Number = 10
this.createTextField("my_txt", 1, 100, 100, 300, 100);
my_txt.text = "闪吧！！动态文本alpha变化！";
my_txt.filters = [txt_blur];
onEnterFrame = function () {
        my_txt._alpha -= speed;
        my_txt._alpha<=0 || my_txt._alpha>=100 ? speed=-speed : 终极讨厌;
};