This paper presents a novel readout system for wireless passive pressure sensors based on the inductively coupled inductor and cavity (LC) resonant circuits. The proposed system consists of a reader antenna inductively coupled to the sensor circuit, a readout circuit, and a personal computer (PC) post processing unit. The readout circuit generates a voltage signal representing the sensor’s capacitance. The frequency of the reader antenna driving signal is a constant, which is equal to the sensor’s resonant frequency at zero pressure. Based on mechanical and electrical modeling, the pressure sensor design based on the high temperature co-fired ceramic (HTCC) technology is conducted and discussed. The functionality and accuracy of the readout system are tested with a voltage-capacitance measurement system and demonstrated in a realistic pressure measurement environment, so that the overall performance and the feasibility of the readout system are proved.