Abstract: Switch-zoom optical system is composed of the subsystem with wide field of view and the subsystem with narrow field of view. Due to the errors from many aspects such as the refractive index of optical material, the optical manufacturing and assembling, the actual image surfaces of both subsystem deviate from their ideal image surfaces, and the drifts are different, that is, the two subsystems are not confocal. To solve the problem, a variety of confocal design schemes, the selection principle and an optimal scheme which fixed long focus and adjusted short focus, adjusted the compensating set for a mid-wave infrared (MWIR) switch-zoom optical system were given.