The invention relates to a magnesium ingot casting machine, in particular to a small-size magnesium ingot casting machine. The small-size magnesium ingot casting machine comprises a heat-preservation furnace, a heat-preservation pot, a plurality of moulds, a machine frame, a horizontal conveying mechanism and a driving mechanism, wherein the heat-preservation pot is sleeved inside the heat-preservation furnace and used for containing molten magnesium, the horizontal conveying mechanism is arranged on the machine frame and the driving mechanism is connected with one end of a lever rocking arm and drives the other end of the lever rocking arm to swing up and down in a reciprocating mode. The horizontal conveying mechanism comprises two drive sprockets, two driven sprockets, two conveying chains, a motor and a speed reducer, wherein the two drive sprockets and the two driven sprockets are respectively arranged at the front end and the rear end of the machine frame, the speed reducer is connected with the motor and is connected with a sprocket shaft of the drive sprockets through a coupler, a large sprocket is arranged on the sprocket shaft of the drive sprockets, the two conveying chains are respectively meshed with chain teeth at the corresponding side of the two drive sprockets and the two driven sprockets, a bearing panel is connected between every two opposite chain sections of the two conveying chains, one mould is fixedly arranged on each bearing panel, and a linear motion track among the moulds is guaranteed.