In this study, we designed a heat exhaust scheme for an underground cooling tower combined with a practical underground building to complete thermal performance tests on cross-corrugated organic paper filler to obtain an experimental correlation equation of the filler's bulk mass coefficient. The results show that the scheme of this underground cooling tower meets the requirements of heat exhaust, but the system is challenged by high air resistance and low filler utilization. To overcome this problem, an experiment to determine the filler volume was conducted. Considering that the experimental process for determining the heat performance of traditional cooling tower filler is complicated and multiple physical quantities are required for strict control when performing a single factor experiment by using an analogy of the direct evaporative cooling process, we determined the relevance between the saturation efficiency and bulk mass coefficient in the evaporative cooling process and describe a new method to determine the bulk mass coefficient. The results of the calculation agree with the experimental results.