The mirror holder is a device in common use for many instruments.It is necessary thatthe mirror holder has a well adjusting performance so as to tune light path of the instrumentsmoothly.In line with this a construction of the mirror holder is proposed. Performance ofthe adjusting machine of the construction is analysed by using displacement resolutionmethod.Theortical analysis and practical application show that the mirror holder has excellent performance which insures orthogonal independence between two dimension of movement of light patch in small range.The mirror holder shields the light through hole least.Theholder is constructed simple and cost low. It may be uesd in many instruments conveniently.