The ordering behavior of the L12 type Co3Ti-based intermetallics were studied by using the sublattice model supported with first-principles calculations. The results show that the stoichiometric intermetallics Co3Ti is fully ordered intermetallics, where Co atoms always occupy the 3c sublattice and Ti atoms always occupy the 1a sublattice. For ternary alloy Co72Ti24M4, where xCo/xTi=3:1 and M represents the ternary alloying element, when M represents Si, Ta or Ti atom, M occupies 1a sublattice, while when M represents Cu, Ni, Pd, Rh, V or W atom, M occupies 3c sublattice, and when M represents Al, Cr, Ge, Mn, Sc or Y atom, M occupies both 1a and 3c sublattices. The site preferences of these alloying elements are independent of the heat treatment temperature. While the site occupancy of ternary alloying element Fe, Hf, Mo, Nb, Ru or Zr in ternary alloy Co72Ti24M4 varies with the heat treatment temperature. With the increase of extranuclear electrons, the site preference of the transition metal tends to change from 1a sublattice to 3c sublattice gradually. The sublattice occupancy fractions varying with alloy compositions and temperature were also calculated in some other Co3Ti-based alloys where xCo/xT offsets 3:1. The predicted results are consistent with most of the literatures, and some disagreements in literatures were clarified