Gas-assisted atomization is commonly seen in fuel injection systems, where the breakup and atomization of a liquid jet is assisted by a coflowing high-speed gas jet. In this paper, three-dimensional direct numerical simulations (DNS) are performed to investigate the characteristics of turbulent multiphase flows in gas-assisted atomization. Although many numerical simulations of atomization have been reported in the literature, whether the atomization characteristics such as droplet formation and size distribution are fully resolved is often unclear. In the present study, particular attention is focused on the effect of the grid resolution on the deterministic and statistical atomization characteristics. The statistical characteristics of the turbulence (such as turbulence kinetic energy) and of the spray (such as droplet size distribution, liquid volume fraction, and gas-liquid interfacial area) are calculated by averaging the DNS data. The complex interaction between the interfacial waves and the gas turbulent jet is shown to have a significant impact on droplet formation.