A wireless data terminal device comprises a detachable USB connector and a main circuit board, where at least two redundancy grounding connections are provided between the detachable USB connector and the main circuit board, and the grounding points of the at least two redundancy grounding connections are not adjacent to each other. A method for improving the radio performance of the wireless data terminal device is further provided. With the wireless data terminal device or the method for improving the radio performance of the wireless data terminal device, the connection of the grounding plane of the wireless data terminal device with the grounding plane of a computer is effectively enhanced. Therefore, the radio performance of the wireless data terminal device is improved.