A synchrotron radiation experiment and a large-scale simulation are indispensable for development new functional rubber materials in recent years. In this series of lectures, I will try to explain about an analysis of structure of filled rubber vulcanizates by cooperation of a synchrotron radiation experiment and a large-scale simulation. In this first article, I will discuss an ultra-small angle X-ray scattering experiment of end-modified styrene butadiene rubber, and a reorganization of filler structure by large- scale reverse Monte Carlo simulation using this experimental data.