I am new in Blackberry. so can anyone help me out for following queries. Which SDK is used in Blackberry? in Which language Black Berry application develope? and Can we call Web service through BlackBerry application?
Blackberry applications are written in Java. They support Java ME as well as some additional blackberry specific APIs. Check out http://na.blackberry.com/eng/developers/javaappdev/overview.jsp
As for calling a web service, yes you can do that as well. Check out the Rapid Application development tutorial at: http://na.blackberry.com/eng/developers/rapidappdev/
As heavyd said you can use the Rapid Application Development for accessing web services.
I've used the Visual Studio plugin before but this doesn't allow you as much access to the API as using the standard JDE plugin for Eclipse or the Blackberrys Java Development Environment (at least when I used it). It all depends on what you want to do, whether it's whip up a quick app or create a fully customised sweet looking application that'll take a little longer.
If you don't decide to go down the RAD route you can use a 3rd party library like KSOAP2, or, the way I do it, is use the Sun Wireless Toolkit (WTK) to create Stubs for you're web service methods which you can then call in your application. I've used this method for a .NET web service and it's pretty straightforward.