Abstract: Calibration specification is the base for carrying out the calibration. Drafting the calibration specification of IR optical focal length measuring equipment is a very important object, it is the basic requirement for metrological assurance. The calibration specification of IR optical focal length measuring equipment not only applying to metrological service, to guarantee the accuracy, compatibility and traceability of daily calibration works, but provided the technology basis for the branch that produces infrared optics system focal distance measuring device, at the same time satisfies request of the consumer who use the infrared optics system focal distance measuring systematic in the process applying for various attestation. In this paper, construction, methods of calibration, and evaluation of uncertainty of the calibration specification for IR optical focal length measuring equipment are described.