Abstract: XRFS was applied to the determination of tantalum (wTa 0.1%-8.50%) in nickel, cobalt and iron based alloys. Through comprehensive consideration, the spectral line of Lβ1 of Ta was chosen as analytical spectral line, and background site of 2θ of 39.50° was selected. Three common alloying elements (i.e. Nb, Hf and W) commonly present in the 3 kinds of alloys were found to interfere the determination of Ta by overlap of their spectral lines of Kβ1 (of Nb), Lβ2 (of Hf) and Lβ4 (of W) with the Lβ1 of Ta chosen for the determination. On the base of values of overlap interfering coefficient K of the 3 elements found by using appropriate standard samples, and by using the FP method with help of the FP-software, the above mentioned interferences were eliminated. 11 standard or known samples were analyzed by the proposed method for their Ta contents ranging from wTa 0.015%-4.81%, the results found were in consistency with the certified values or known values. Test for precision was made on 2 of the 11 samples, giving values of RSD′s (n=7) of 0.46% (wTa=4.278%) and 9.9% (wTa=0.020%).