Based on the multiconfiguration Dirac-Fock method, with the recently developed program for the calculation of cross section of dielectronic recombination (DR), the KLL DR process of highly charged mercury and uranium ions from helium-like to boron-like have been systematically studied. For Hg ions, the contributions to the level of doubly excited state from Breit effect and quantum electrodynamic (QED) effect, KLL DR resonant energies, total line width and corresponding DR resonant strength have been calculated and analyzed. A good overall agreement was found between the present calculations and the previous theoretical and experimental result. Based on the calculation of Hg ions, the KLL DR process of highly charged uranium ions was studied theoretically. The comparison of present results with the other theoretical and experimental results has been made.