Abstract: For the spiral tube heat exchanger with smaller diameter and more complex structure, using the conventional method is not an effective way to clean the inside of the tubes. In this paper, regarding the difficulties in cleaning the steam generator of high-temperature gas cooled reactor (HTGR), on the basis of the numerical model established for calculating the purging resistance of spiral tube heat exchanger, the effects of steam purging and compressed air purging are analyzed and compared respectively. Based on the calculation results, the compressed air is chosen as the purging media and then the purging process is tested and verified. The study results show that compressed air purging can meet the cleaning requirements of the relevant standards, while steam purging will probably make the tubes expand unevenly. Therefore, compressed air purging is recommended as the first choice.