For calibration and intercomparison experiments, a thoron chamber with an inner volume of 300 l was designed based on a programmable constant temperature and humidity testing device in this work. The commercial lantern mantles enriched with (232)Th were used as the (220)Rn source and the mantles were set in 3×3×3 points of lattice style inside the chamber. Experimental studies showed that (220)Rn concentrations in the chamber could be easily controlled and adjusted from about 0.5 to 80 kBq m(-3) through manual settings of the relative humidity and temperature, and the spatial distribution of (220)Rn in the chamber was fairly homogeneous.