RECS (Robot-Environment Compromise System) means the technology to compromise the robot and environment in order to increase the robot performance. In near future multipurpose robot unlike industrial robot is indispensable for social needs, welfare robot for example, and this type of robot requires high robot technology. However we cannot hope the establishment and practice of this high technology with enough reliability in near future. RECS makes it possible to develop the practical multipurpose robot by setting the environment so as that the robot can recognize and act skillfully to the object needed. In this paper RECS concept is proposed, and the advantage, limit of change of environment apt to robot, new robot technology uniquely for RECS are made clear. Indoor mobile robot system is developed according to the RECS concept, and experiment proved the practicity of RECS.