Research methods: This paper, based on the field observation information of thermal probes subgrade in Qingshuihe experimental section along Qinghai-Tibet Railway in permafrost area, calculates effective range of transferring heat of thermal probes in cold season during 2002-2003，the maximum effective range of transferring heat, producing cold quantity of thermal probes and decrease value of soil mass in thermal probes evaporating section in effective range of transferring heat. This paper also puts forward vertical space adopted in thermal probes design.
Research results: (1) Effect of effective range of transferring heat of thermal probes is 1. 50 m and maximum effective range of transferring heat is 2. 16 m in natural ground surface in Qingshuihe experimental section; ( 2 ) Producing cold quantity of thermal probes in cold season is 1 149 MJ in total during working; ( 3 ) Decrease value of soil mass in thermal probes evaporating section within effective range of transferring heat is 0. 95oC.
Research conclusions: Vertical space of thermal probes in engineering design is 3. 0 m in order to ensure soil mass temperature to highly decrease within effective range of transferring heat of thermal probes.
2007, Vol. 24 
