I want to use ip camera as webcam in my application. is there an application to create virtual webcam and could add ip for work?
You've not specified what camera you're looking at or what operating system or language you're programming in so this addresses the general case:
With most IP cameras it's normally far easier to just pull the frames off the IP camera directly within your application. Typically that would be with an HTTP GET request which can be done with something like libcurl. This is much simpler than most camera interfaces for directly connected cameras since all of the encoding and capture options, device opening/closing get handled for you and what you receive is a JPEG or similar.
If you really want to make a virtual camera device this is pretty easy on Linux, e.g. with something like v4l2vd, you need to write a bit of glue to connect that to your desired source, but it's fairly simple and what you get at the end of it looks like any other V4L2 device.