Abstract: Tests were conducted for the purpose of comparing TP304H and TP347H hi- pressure boiler tubes made by No. 5 I & S Group Co.,Shanghai and those by Sumitomo Metal Ltd, Japan, covering chemical composition, mechanical properties and structures and grain sizes after solid solution aging treatments under different temperatures and focusing on effects l,y different solid solution temperatures on grain size and mechanical properties of the tubes. The results show that the Japan-made tubes are a little bit better than the China-made tubes in terms of grain size and grain uniformity, while the latter are completely up to ASME-SA213 Spec. and the Chinese GB5310 Spec. and relevant agreement specification in terms of all the properties.