The purpose of the research is to verify the viability and the applicability of TPCT (two-phase closed thermosyphon) sucker Rod in cyclic steam stimulation for heavy oils. On the basis of the previous researches and the basic principles of TPCT, the laboratory experiment system was setup and the heat-transfer experiment was conducted using liquid ammonia as the working fluid. The laboratory data shows that TPCT sucker rod can utilize the heat energy from hot water depending upon the vaporization and condensation of ammonia to transfer heat Based on the results from the laboratory experiment, the site application of TPCT sucker rod was undertaken in well H127-26-34 of Liaohe Oilfield in China. The site application results demonstrate that TPCT sucker rod can decrease the heat loss of fluids in wellbore and improve well performance during cyclic steam stimulation. (c) 2013 Elsevier Ltd. All rights reserved.