MEMS (Micro Electro Mechanical Systems) technology could he applied on bio-chips to measure and detect micro objects. Generally, the detected signal is so small that we need to amplify it for next processing (such as A/D converter). In this study, we develop a trans-impedance amplifier (TIA) circuit to detect the blocking conductance when particles across an ion-pore. Consider the simple circuits, simple manufacture process, and the capability of integrating with MEMS process, The TIA circuit and the MEMS ion-pore is designed based on 0.35um CMOS process. The measured results of this amplifier are 94dB Omega high gain, low noise as the M.D.S. of 25nA, and the bandwidth larger than 15MHz.