Granular computing is an emerging conceptual and computing paradigm of information processing. Just as a great umbrella, it may be regarded as a label of theories, methodologies, techniques, and tools that make use of information granules. Extension set theory is a new computational method of knowledge resolution and the significance of attribute. Extension method can be used to describe the thinking process associated with both quantitative change and qualitative change. In this paper, we integrate granular computing with extension method. We utilize the extension method to solve some problems for communicating between information granular worlds. The communication procedures between information granular worlds based on extension method can be established, which is valuable and easy to implement in computer.