The invention discloses a precision instrument guide rail system based on circular rolling element array arrangement and cambered surface clamping and positioning and belongs to the technical field ofprecision instruments and machines. A guide rail component is provided with four working faces, the middle area of each working face is of a groove structure, and each working face is symmetrically provided with two coplanar boss working belts of equal height. A guide rail rack component is composed of four supporting guide plates, and each supporting guide plate is provided with a rolling element set which comprises three rolling unit arrays distributed in a triangle mode. Each rolling unit array is formed by densely distributing a plurality of rolling elements. A sensor clamping and lockingcomponent comprises a clamping matrix, a clamping moving body and a clamping feeding mechanism; the clamping matrix is provided with a long-strip-shaped arc hole, a threaded hole and an arc groove; and the clamping moving body moves in the long-strip-shaped arc hole under the action of the clamping feeding mechanism so that a sensor can be locked or released. The precision instrument guide rail system integrates the characteristics of high precision, high rigidity and the clamping and locking features.