Taking 3104 aluminum alloy for can body as object， offline inclusion analysis was carried out using PoDFA （Porous Disc Filtration Apparatus）， focusing on the identification of type and content of inclusions at different locations of casting line. The results indicate that for 3104 ingots produced by electrolytic aluminum alloying， the inclusions at the exit of the holding furnace are mainly composed of TiB

2

and spinel particles， and the content is high， which is 0.202 mm

2

/kg. After online degassing， the content of TiB

2

and spinel is decreased to 0.129 mm

2

/kg， however， the overall content remains high with the same inclusion type. After deep-bed filtration， the inclusion is predominately spinel with content further decreased to 0.031 mm

2

/kg. By properly reducing the temperature of the melt in the holding furnace， prolonging the holding time， and adding CFF before deep-bed filtration， the melt quality of 3104 alloy is effectively enhanced， significantly reducing the rate of broken can during the subsequent punching process.