The invention relates to a negative electrode metal cap structure part of a button-type lithium battery. A method for preparing the negative electrode metal cap structure part of the button-type lithium battery comprises the following steps: stamping and cutting a circular material to form a circular plate; deep drawing and punching the circular plate to form an L-shaped bent portion including a vertical portion and a horizontal portion at the outer edge of the circular plate; deep drawing and punching the horizontal portion of the L-shaped bent portion to form a first bent portion; performingfirst stamping folding for overlapping of the bent portion and the unbent portion of the horizontal portion to jointly form a first folded portion; and performing second stamping folding for overlapping of the first folded portion and the vertical portion to jointly form a three-layer folded portion which is vertically disposed to complete the preparation of the negative electrode metal cap structure part of the button-type lithium battery. Through the above steps, the strength of the whole negative electrode metal cap of the button-type lithium battery can be effectively enhanced, the packaging performance is improved, and the quality of the finished product of the button-type lithium battery is improved.