Disclosed in the present invention are a self-assembled serially-connected cell-penetrating peptide nano-particulate antibacterial agent capable of penetrating the blood brain barrier, a preparation method therefor, and uses thereof. The general structural formula of the antibacterial agent is Cn-X-Y, wherein X and Y are both cell-penetrating peptides and are serially connected to form a hydrophilic portion, and the Cn represents a hydrophobic portion fatty acid chain coupled with the cell-penetrating peptides; the cell-penetrating peptides are L-type amino acids; and the number of carbon atoms of the fatty acid chain is 12-20. The self-assembled serially-connected cell-penetrating peptide nano-particles of the present invention have good resistance to bacteria (including drug-resistant bacteria) and fungus, can penetrate the blood brain barrier, has low hemolytic toxicity, and can be used for researching and developing novel antibacterial agents for treating brain infection and other infectious diseases.