Abstract: Toughness is regarded as one of the critical properties of steel pipes. Based on the results of the toughness tests as made to the LSAW pipes to be used for the Sichuan-East Gas Pipeline Project, the main factors as influencing the fracture toughness of the steel pipes are analyzed, including the chemical composition and micro structure of the steel plate, matching of the welding wire with the welding flux, and the welding heat input, etc. Also discussed are the elements to be controlled for proper fracture toughness of the hi-strength linepipe. The result of relevant fracture toughness test shows that the fracture toughness of the said LSAW pipes is excellent.