In this work, we systematically study the mass spectrum of fully heavy tetraquark in an extended chromomagnetic model, which includes both color and interactions. Numerical results indicate that energy level is mainly determined by interaction, favors color-sextet $|(QQ{)}^{{6}_{c}}(\overline{Q}\overline{Q}{)}^{{\overline{6}}_{c}}?$ configuration over color-triplet $|(QQ{)}^{{\overline{3}}_{c}}...