The blank holder gap is an effective way to control material flow. The effect of this gap on deep drawing of square cups with ETIAL-8 sheets was studied by the experimental approach. Different blank holder gaps ranging from 1 mm to 1.8 mm for 1 mm aluminum sheets were used in the experiments. The experimental implementation shows that a reasonable (optimized, controlled) value of blank holder gap has a great effect on the forming quality of the final part. Finally, a suitable blank holder gap for deep drawing of square cup for given tooling and material is proposed and the reasons of the failure modes are explained.