Abstract: Authors carried out an in-situ prototype test and focused on the thawing process and temperature field varia-tions both by naturally thawing and “naturally+enforced” thawing. The results showed that the time of both modes was shorter than that of other conventional freezing applications since the volume of the frozen soil was small. Hence,the enforced thawing by brine at ordinary temperature achieved some good results. What is more,after releasing the ther-mal insulation curtain in the holly pipe,the thawing rate was high enough so that the enhancing tubes could be turn off. As an important part of the research on the freezing effect of FSPR,this test is the first time to study the thawing rules,which is essential for the subsequent construction.