A portable label printer for printing content onto a surface of a label is provided. The label has a chip disposed therein. The portable label printer includes a main body, an RFID antenna assembly, a front cover unit, a back cover unit, and a print head module. The front and back cover units are disposed in the main body, and a paper exit port is formed between the front and back cover units. The RFID antenna assembly is disposed in the main body and adjacent to the paper exit port. The print head module is disposed in the main body and under the RFID antenna assembly. The label first passes through the print head module, and then passes through the RFID antenna assembly. When the label passes through the RFID antenna assembly, the RFID antenna assembly performs data reading or data writing on the chip of the label.