The problem for me is how to adjust the contrast of the picture, should the rocks brighter than this ? and how about the sky color, is it to saturated or not, please give me your best opinion about the post processing this image.
I think the sky color is fine, I love it. I would use the liquify tool to straighten the horizon somewhat, or at least try to correct it with the Lens Distort tool in Photoshop.
You can actually try burning the rocks a little, I find them a tad too bright for my liking - doing so would also help with contrast issues. Also, perhaps more aggressive sharpening is in order.. THe picture is looking a little soft here.
Your tones are all over the place here. It looks as though your highlights are blown, then recovered --- and your shadow tones were too dark, then recovered. With that sort of sky, I would expect to see some of the color reflected a bit more on the surface of the rocks. You have a lot of potential with this scene, but sometimes even when you use grads, you still need to bracket your exposure for proper foreground/background exposure.
