An underwater towing test device including a driving mechanism, an observation platform disposed under the driving mechanism, a towing member, and a towed body. The driving mechanism includes an operation platform, an extended platform connected to the operation platform, a crane, a first railing, a lifebuoy, a control center, a power distribution room, and a plurality of bus ports. The operation platform includes two rail grooves disposed in parallel and a moon pool provided with two pool slots on both ends thereof. The crane includes a chassis provided with a plurality of first guide rollers. The first railing is positioned along the edge of the operation platform and the extended platform, with the lifebuoy hanging thereon. The control center, the power distribution room, the plurality of bus ports, and the moon pool are fixedly disposed on the operation platform.