An aluminum alloy casting waste gas treating device is characterized in that a gas inlet silencing pipe (2) is welded and introduced to the upper-middle part of a pagoda-shaped spray water tank (1), a U-shaped spiral liquid curtain spray system (3) and a feeding pipe (17) are connected and introduced to the upper part of the gas inlet silencing pipe (2) respectively, and the feeding pipe (17) is integrally connected with a feeding hopper (19) through a feeding valve (18). The aluminum alloy casting waste gas treating device has the benefits that sufficient gas passing cross sections and retention time are provided; good gas flow distribution is generated, so that all gas passing cross sections can be used sufficiently; the device has sound attenuation, noise reduction, strong deodorization performance and high waste gas treating capacity; harmful constituent absorption and purification efficiency is high; an absorption liquid and an adsorbent are recyclable, harmful substances can be changed into useful substances, and secondary environmental pollution is avoided; the structure is simple, and the operation is stable; gas passing resistance is low, and the production efficiency can be increased; the working cost is low, and maintenance is facilitated; the production efficiency can be increased effectively.