Raman integrating sphere consist of confocal Raman scattering exciting and collecting system and four corner cube mirror to increasing optical path system. Confocal Raman scattering exciting and collecting system consists of N collecting optical systems which has the same confocal, and Raman scattering from the confocal to the N collecting optical systems will be collected and transferred to one direction, so the collection efficiency will be enhanced N times. Four corner cube mirror to increasing optical path system consist of 4 corner cube mirrors, and the exciting laser will be reflected by the 4 corner cube mirrors many times and the light path parallel to each other, so all the light will be focused to the confocal by collecting optical systems, and the efficiency of exciting laser power will be increased many times. When Raman integrating sphere is used to detect gases, the advantages include multicomponent detection, low concentration, in situ, high-speed, undamaged, non contact, qualitative analysis, and relative quantitative analysis, and so on.