The present invention relates to a grating scale reliability testing stand and a reliability test method based on a load spectrum, and belongs to a testing device applied to the machinery field. The grating scale reliability testing stand comprises a grating scale main scale installing plate, support blocks, reading head installing plates, towing chains, linear motors, a sliding plate, grating scale main scales, reading heads, base plates and three-directional acceleration sensors. The present invention provides a reliability test method based on a velocity spectrum and an acceleration spectrum. Regulation can be performed according to concrete requirements of a test, such as regulation of an instantaneous velocity, an instantaneous acceleration, an average velocity and an average acceleration of a linear motor and a motion rule curve thereof; the grating scale is tested through simulation of the velocity load and the acceleration load, the velocity spectrum and the acceleration spectrum are complied according to the velocity load and the acceleration load in actual operation of the grating scale, the reliability test based on the velocity spectrum and the acceleration spectrum canreally reflect the velocity load and the acceleration load of the grating scale in the actual operation, and various types of enclosed grating scale reliability tests can be satisfied.