先看看最终效果图

效果预览
1、新建640*460 72pX,颜色任意的画布一个,再新建一空白图层,命名[右面],用钢笔工具作出路径。(图1)

图1
2、对渐变条进行设置。(图2)

图2
3、把路径转换为选区,进行渐变填充。(图3)

图3
4、Ctrl+J复制一层,命名[左面],编辑/变换/水平翻转,再次设置渐变条,再次对其进行渐变填充后移动到左面。(图4)

图4
5、在背景层上面新建一层做路径。(图5)

图5
6、转换成选区后进行渐变填充。(图6)

图6

图7

图8
8、在顶层再新建一层,做路径。(图9)

图9