In this work, we have performed a simulation to study the structural characteristics and phase transformation in Al2O3 glass under compression. The structural characteristics of Al2O3 glass were examined via AlOx units, OAly linkages, the average bond distance distributions, order parameters, and visualization of simulation data. The result showed that the network structure of Al2O3 glass is built mainly by AlOx (x = 3, 4, 5, 6, 7) units that are linked to each other via common O atoms. We found that the distribution of AlOx units in network structure is not uniform but tends to form clusters contained AlOx units. In addition, during a moderately long time, the glass has a two-phase that consists of separate low-density (LD) and high-density (HD) phases. The size of these phases significantly depends on the compression.