This paper aims to determine a computer-aided mold design algorithm for precast concrete products to be produced by external vibrators. For this purpose, the behaviors of two different precast concrete molds were investigated experimentally and analytically. Experiments were performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on the mold while it is empty and full of fresh concrete. Test results indicate that the difference between displacement amplitudes of empty and full molds is considerably high.