Structure and diffusion of liquid Al 2 O 3 have been investigated by molecular dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with the BKS pair potentials. Structure of liquid models agrees reasonably with experiment. The microstructure of systems has been analyzed through partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Temperature dependence of these distributions was obtained. Calculations show that in the liquid Al 2 O 3 model with real density at 2.80 g/cm 3 there is a short-range order dominated by distorted AlO 4 tetrahedron, in agreement with Landron's experiment. Self-diffusion constants have been calculated. The temperature dependence of diffusion constants D in liquid Al 2 O 3 shows an Arrhenius law with activation energy which is close to experimental one for liquid SiO 2 and close to the calculated data for diffusion in liquid aluminum silicate. With increasing temperature we find that this dependence shows a crossover to one which can be described well by a power law, D / Γ°T Γ T c Γ g : The critical temperature T c is about 3500 K and the exponent g is close to 0.50. We also present the effects of MD run time on the structure of models. The phase transition temperature T g for the Al 2 O 3 system is anywhere around 2100 K.