Terahertz spectroscopy (THz) is a brand-new radiation source with many unique advantages. It owns many potential applications in all area. An experiment was carried out on soil heavy metal detection using THz in Jun., 2010 at Oklahoma State University. Two types of sample holders (1.5mm thickness and 3 mm thickness) were designed based on specific requirements and applications in this paper. The optical material, size, thickness of the sample, thickness of the side-wall, property of samples for holding, adhesive materials, cost were discussed in detail; then, an integrated description were given and a 3-D model was established. Real holders were manufactured based on the former design and their THz characteristics were measured. At last, the holders were used in the current soil heavy metal detection experiment. The results showed that, the designed holders showed low absorption of THz and low reflection. Two thickness samples holders all performed well in the experiments, however, for the soil measurement, the sample information could not be completely collected before echo wave came. The 1.5mm thickness holder was selected in our experiment. The designed sample holders are feasible and this research provides a good solution for the difficulties we met in our experiment.