Wu jie,
I'll paste this directly from the Readme file from ArcSWAT 2.1.4a.
In order to install ArcSWAT for ArcGIS 9.2, you MUST have:
1.) Microsoft Windows XP or Windows 2000
2.) ArcGIS 9.2 with SP6 (build 1500)
3.) ArcGIS Spatial Analyst 9.2
4.) ArcGIS Dot Net support (usually found in: C:\ProgramFiles\ArcGIS
\DotNet)
5.) Microsoft .Net Framework 2.0
6.) Adobe Acrobat Reader Version 8 or higher. Acrobat Reader may be
downloaded for free from:
http://www.adobe.com/products/acrobat/readstep2.html
Regards,
Kyle