In this study, the adsorption of different degree of polymerization of carboxymethyl dextran (CMD) on three calcium carbonate crystal surfaces is investigated by molecular dynamics simulation. The results shows that CMD can be firmly adsorbed on the calcium carbonate crystal surfaces, change their normal growth characteristics, displace the water molecules near the crystal surfaces, and prevent the nucleation of calcium carbonate. CMD can form a dense self-assembled isolation film on the calcium carbonate crystal surfaces to prevent further growth of the crystal surfaces. The results revealed that at a simulation system temperature of 303 K, the oxygen atoms in the carboxyl groups of CMD regularly observed at a distance of 2.0 − 3.1 A from the calcium ions in the calcium carbonate crystal surfaces. With the increase in the degree of polymerization (DP), the binding energy increases, as well as the adsorption strength and adsorption probability of CMD on different calcium carbonate crystal surfaces and the scale inhibition efficiency. In the case of different calcium carbonate crystal surfaces, binding energy decreases in the order of vaterite (110) > aragonite (010) > calcite (104). The inhibition of carboxymethyl dextran on calcium carbonate fouling can protect the heat transfer surface from calcium carbonate erosion and improve its heat transfer performance. This is of great significance for prolonging the service life of heat transfer surfaces, increasing heat transfer efficiency and reducing economic losses.