A hard drive rack ventilation structure includes a primary rack, a plurality of secondary racks and hard drive units. The secondary racks are stacked in layers and assembled inside the primary rack. Each secondary rack includes a top portion and side portions extended downward from two sides thereof, and the two side portions include corresponding sliding tracks thereon. The hard drive units are installed on the sliding tracks of the secondary racks. Each hard drive unit includes a hard drive main body and a handle installed at a front thereof. A gap is formed between the handle and the hard drive main body. A top front edge of each secondary rack includes a hollow portion formed corresponding to the gap of each hard drive unit. The hollow portions and the gaps of the hard drive units are fluidly and vertically connected to form an airflow ventilation channel.