Abstract: The uniform design method was used to design the sintering flux for X100 pipeline steel, and five fluorine alkali fluxes with high basicity in couple with welding wire were tested by automatic submerged arc welding.The tensile properties, metallographic structure, hardness value, impact value, impact fracture appearance were analyzed for two kinds of fluxes.The result shows the addition of the appropriate amount of MnO has greater effect on process of flux and toughness of joint.It can improve the weld depth, increase the liquidity of the slag, restrain the undercutting.Meanwhile, it can inhibit the formation of high temperature ferritic structure and be beneficial to the formation of acicular ferrite.In all of five fluxes, the comprehensive performance of No.2 welded joint is the best, which meets relevant technical standards.