Low dimensional heterojunctions have many unique physical and thermal characteristics, arousing great interests in the thermal management of advanced semiconductor devices. We investigate the heat transfer across a one-dimensional heterojunction by the reactive force field molecular dynamic simulation. This heterojunction is constructed by a carbon nanotube and a boron nitride nanotube by covalent bonding. The intrinsic carbon nanotube and boron nitride nanotube are good heat conductors with interesting phonon transport behavior. This one-dimensional heterojunction would be a potential candidate to study nontrivial heat transfer properties. By the molecular dynamic simulation, the interfacial thermal conductance shows a divergent trend with the system length when heat flux flows from the boron nitride nanotube region to the carbon nanotube region. Our simulation predicted a divergent exponent (0.49), which is close to the divergent exponent (2/5) estimated from the superdiffusive theoretical model. The analysis of the mean square displacement of particles confirms a connection between the anomalous particle diffusion and the superdiffusive heat transport. This result reveals the extraordinary phonon manipulation function of the heterojunction and indicates the potential application in efficient heat management of nano-size devices.