The invention relates to an aluminum alloy heat dissipation device with automatic sealing mechanisms. The aluminum alloy heat dissipation device with the automatic sealing mechanism is characterized by comprising a heat dissipation base, a plurality of cooling fins, the plurality of automatic sealing mechanisms and a plurality of screws, wherein a first water guide hole and a plurality of auxiliary cavity holes are formed in the heat dissipation base, the auxiliary cavity holes comprise left vertical holes, middle vertical holes, right vertical holes and inner cavities, second water guide holes and jacking columns are arranged on the cooling fins, all the automatic sealing mechanisms are mounted in the inner cavities in a one-to-one correspondence manner, the automatic sealing mechanisms comprise sealing parts and jacking springs, the sealing parts comprise sealing pressing plates, flow guide blocks, guide columns, left flow guide cylinders and right flow guide cylinders, and all the cooling fins are arranged on the top surface of the heat dissipation base. According to the aluminum alloy heat dissipation device, enterprises can select a proper number of cooling fins according to actual heat dissipation requirements, the use is more flexible, and the cost input of the enterprises can be greatly reduced; and the aluminum alloy heat dissipation device further has the advantages of being simple in structure, high in reliability, good in heat dissipation effect, low in maintenance cost and the like.