Abstract: According to the physical and chemical properties of the common composition of agglomerated flux-MnO, three kinds of agglomerated flux were prepared and the parallel tests on weld microstiuctures and the mechanical property were discussed also.The result shows that the addition of MnO in the agglomerated flux not only incneases the alkalinity of the flux and its reducibility, and purifies the weld, and improves the slag detachability and the formation ability and processing abilities, but also can stabilize the austenite, and reduce the γ※αtransformation temperature by controlling the quantity of Mn in the weld metal when MnO is added in, which will make a good environment for the formation of the acicular ferrite and the promotion of the mechanical property of the weld metal.