The present invention relates to a radiation measurement instrument calibration facility with the abilities of lowering scattered radiation and shielding background radiation and it is capable of providing a suitable environment for performing performance test, calibration and experiment upon a radiation measurement instrument. In an embodiment, the calibration facility comprises: a shielding device, a collimator, a multi-source irradiator, a radiation baffle, a carrier, an electric door unit and a control unit. With the design of the calibration facility of the present invention, the interference coming from the background radiation and scattered radiation in the laboratory during the radiation measurement instrument calibration can be effectively reduced to enhance the accuracy of measurement or calibration for the instrument, and also the instrument calibration and testing can be performed in radiation fields of low-, medium- and high-dose rate levels to meet the requirements of ISO 4037-1 (1996) Standard.