The present invention provides an antibody or antibody fragment capable of binding to lung-specific X protein, which can be used for antitumor, and uses thereof. The antibody or antibody fragment comprises heavy chain CDR amino acid sequences SEQ ID NO: 1, SEQ ID NO: 2 and SEQ ID NO: 3, and light chain CDR amino acid sequences SEQ ID NO: 4, SEQ ID NO: 5, and SEQ ID NO: 6, or heavy chain CDR amino acid sequence SEQ ID NO: 1, SEQ ID NO: 7 and SEQ ID NO: 3, and light chain CDR amino acid sequence SEQ ID NO: 8, SEQ ID NO: 5 and SEQ ID NO: 6. The antibody is a chimeric antibody. [Selection] Figure 1