Based on the X-ray diffractometer in the lab, the calibration experiment of the fading curve of the imaging plate (IP) was introduced. The type of the sample was Fuji SR-2025 and the concerned signals were X-rays. A Cu X-ray tube was used as the X-ray source in the experiment while a trihydroxymethylaminomethane (TAM) crystal was used to provide Kα monochromatic radiations. The type of IP scanner was BAS-5000 and the environment temperature was (20±1) ℃. Under the conditions that the X-rays were stable, the spatial uniformity and the line response of the IP were examined well, and the fading curve of the IP was obtained by exposing the IP on different place in different time. Fitting analysis of the fading curve was carried out and the uncertainty was discussed. The experimental results show that the instability of X-ray source is 0.7% and the spatial uniformity of IP is less than 1%; excellent linear response of the sample is also proved; at the energy point of Cu-Kα 8 027.84 eV, the fading curve of the IP decreases slowly in exponential form η(t)=0.36884·exp(－t/159.647 56)+0.633 72; the recorded signals remain 80% while 125 minutes after exposure with visible light shielding.