Tests of capillary radiant cooling system in Chongqing were carried out and thermal parameter were analyzed in conditions of three different capillary laying modes (ceiling, wall and floor) with 18℃ supply water temperature. It concluded that when capillaries were laid on the ceiling, wall and floor respectively, the average temperature of working area was 26.27, 27.22 and 26.57℃ respectively and the radiation surface temperature was 20.96, 21.14 and 22.76℃ in turn. By calculation, the PMV of three conditions was -0.27, 0.32 and -0.2 PPD results were 7.06%, 7.47% and 6.34% respectively. It illustrated that all three laying ways at this experimental conditions could meet the air temperature requirements (no more than 28℃) and PMV, PPD attain thermal environment category I.