Abstract: Production and effective factors of the liquation crack in the welding HAZ of the high temperature nickel base alloys were systematically investigated. The results showed that there were segregation phenomena of Nb, Ti and C on the surface of the liquation crack fracture, and the reasons causing liquation cracking were different for different alloys. By regression analyzing on nine elements within twenty kinds of alloys, the susceptibility coefficient P_LC of liquation crack in HAZ had been obtained.