Abstract: In this paper, in view of the problem that the individual and environmental dose monitoring measurements cannot be calibrated in real time under special environments such as space radiation, nuclear power ocean and nuclear emergency, a portable β irradiator was developed, which could be carried to the site to calibrate the optically stimulated luminescence dosimeter (OSLD), and provide measurement guarantee for the accuracy of dose monitoring in special environment. The β irradiator uses a replaceable ⁹⁰Sr-⁹⁰Y flat plating source as a calibration source and can be traced back to the standard β radiation field. The irradiation action can be controlled through solenoid valve, and the total mass of β irradiator is less than 3 kg. The results show that the dose equivalent rate around β irradiator is at the ambient level, the average dose rate of the reference point is 0.060-0.083 mGy/s, the relative standard uncertainty is 6.9%, and the repeatability of irradiation dose is 3.9% (n=10).