A solution scheme that can inextenso verify electro-optical distance mster and the EDM system of electronic total stations inside a laboratory by establishing fictitious outdoor length standards with two plane mirrors in which the ray will be reflected repeatedly has been proposed in this paper. The difficulties that the scheme will have to solve, have been discussed and the feasibility has been demonstrated with existing technology and experience. Detailedly the extend uncertainty about measurement result of 1000 m by this method has been analysed and accurately calulated, and has got the conclusion that the scheme is feasible entirely.