Requirements acquirement is the first phase of requirement engineering, and there are already many methods to achieve this task. But it should be admitted that requirement acquirement is still a big challenge for developers. Combing with the advanced ideas and efficient practice of XP and considering the current users' features, a new method of two-world simulation is put forward here to obtain more accurate requirements in shorter time. The two-world simulation is composed of two steps filled with iteration. One is about the real world simulation with the main technology of scene analysis, and the other is about the computer world simulation with the main technology of fast prototype. This method could be applied to the development of small or medium size projects with changeful requirements. And it has successfully used in some system development. It could also provide some suggestions for other developers to make the requirements acquirement easier.