Currently Being ModeratedDec 5, 2012 6:42 AM (in response to Kano Zhang)
Try one of the several third-party apps that can open Excel documents. You might have better luck with one of those. Ones often recommended include Documents 2 Go, Quickoffice and Office2 HD. If those don't work and you can accept needing a network connection whenever you want to use an Excel document, a server-based solution such as CloudOn might be an option for you.
Note that according to that article even Microsoft's own Windows Phone 6 has problems, so this may be an issue with SSRS generating non-standard files.