The invention relates to an automatic proportioning device for clay slurry, which is characterized in that a weighing hopper is connected with a support frame through a weighing sensor; an overflow pipe, a liquid level sensing device, a raw slurry delivery pipe and a clear water delivery pipe are arranged in the weighing hopper; the raw slurry delivery pipe and the clear water delivery pipe are connected with a raw slurry pump and a clear water pump respectively; the raw slurry pump and the clear water pump are controlled through an industrial personal computer; the raw slurry is delivered to the weighing hopper; the proportion of the clay slurry in the weighing hopper is measured by a weighing sensor; and the clear water is added according to a set value till the proportion is consistent with the set value. The automatic proportioning device can automatically proportion the clay slurry according to the setting requirements.