Abstract: The horizontal twin roll casting-rolling process of AZ31 magnesium alloy was simulated by finite element software. The effect of casting-rolling speed on the solidification welding line characteristics was studied. The results show that the casting- rolling speed has a decisive influence on the position and shape of the solidification welding line. With the increase of casting-rolling speed, the solidification welding line moves towards the exit along the casting-rolling direction, while the edge stress of the casting-rolling plate decreases significantly, which effectively alleviates the edge crack of magnesium alloy casting-rolling.