A wireless signal emitter of a tire pressure detector includes a controller, an antenna, and an impedance matching module. The impedance matching module includes an impedance matching circuit and an impedance adjusting circuit. The impedance matching circuit is electrically connected to the controller. The impedance adjusting circuit is electrically connected to the antenna and the impedance matching circuit. The impedance adjusting circuit includes a switching element electrically connected to the controller. When the switching element receives different signals of the controller, the impedance adjusting circuit switches between two different configurations, so that the impedance matching module has two different impedances, thereby the antenna sends two different radio frequency signals to achieve a purpose of a single tire pressure detector suitable for in-car receivers of different frequencies.