This paper discusses a model of web caching. The model consists of four main elements: web server, DNS server, cache server, and terminal. Each element consists of some components. One element, cache server, has been selected to be discussed in detail. The model was built using TCOZ notation, which is very suitable for defining active objects (components). It is clearer and easier to learn this model, which is a complement to the existing "plain text" model defined in HTTP document. Last but not least, the model can be extended easily for future developments.