This research is an experimental study of the liquid desiccant system performance. In the absorber, dehumidification process and sensible cooling of outdoor air takes place at the same time. The dehumidification effectiveness variation with the chilled water temperature changes in the absorber based on the experiment data collected from the liquid desiccant system operation. The liquid desiccant system used in this research dehumidifies $2000m^3/h$ process air and 24.5kW air-cooled chiller or 136.1kW cooling tower may provide chilled water at target temperature. Experiments were conducted on the day of peak cooling load of outdoor air in the summer season when the outdoor air was hot and humid(at Incheon, South Korea. Aug 2013). Based on the experiment data showing the dehumidification performance variation of the liquid desiccant system for the cooling water temperature, a validation of the dehumidification effectiveness values of a liquid desiccant system is compared with existing model.