Trash bag

A plastic trash bag, comprising:

• a bag body being formed of plastic material and having a first bag sheet overlapping with and attaching to a second bag sheet, a cavity being formed between said first and second bag sheets;
• and
• a tying element impermanently provided with said bag body, wherein said tying element, having a double-layer structure, comprises a first tying band and a second tying band, which is identical to said first tying band, overlapping with said first tying band to enhance the strength of said tying element, wherein a bottom edge of said first tying band is tearably extended from a top edge of said first bag sheet, wherein a top edge of said first tying band is integrated with a top edge of said second tying band,
• wherein said tying element further has a sealing line provided therealong to permanently seal said first tying band with said second tying band, wherein said sealing line is extended parallely and is located close to said bottom edges of said first and second tying bands, wherein said first and second tying bands are permanently overlapped that said top edges of said first and second tying bands are integrated with together and said bottom edges of said first and second tying bands are sealed by said sealing line to ensure said double-layer structure of said tying element after said tying element is torn from said bag body,
• wherein said bottom edge of said second tying band is unattached from said top edge of said second bag sheet to form said top opening of said bag body, wherein when said bottom edge of said first tying band is torn from said top edge of said first bag sheet, said tying element is detached from said bag body to tie a knot at a neck portion of said bag body and to seal said cavity, wherein said bag body is adapted for placing a container that said tying element is located out of said container, wherein said tying element is torn from said bag body without taking said bag body out of said container in order to tie said knot at said bag body.