The present invention relates to a method and device of obtaining a beam hardening correction coefficient for carrying out beam hardening correction on computed tomography data. The method includes the steps of: firstly, acquiring an original reconstructed image and an original sinogram of an object of a particular size secondly, obtaining an error-reduced sinogram after processing the original reconstructed image by error reduction thirdly, sampling and calculating an average value of the original sinogram and an average value of the error-reduced sinogram fourthly, optimizing the original sinogram according to the error-reduced sinogram to determine a coefficient vector of optimization function for the object of the particular size and finally fitting the coefficient vector of the optimization function of the original sinogram to obtain the beam hardening correction coefficient for the object of the particular size.
