This paper discusses the high-bandwidth trans-impedance amplifier combined with data acquisition system with high sampling rate for building nanopore system detection platform. The measured currents vary from 1 pA to nanoamperes and the output voltage is processed by computer. The amplifier must be constructed in multi stages and the key point for designing this amplifier is the low noise technique, especially for the head stage. For application of the nanopore system in single molecule detection, this amplifier can achieve the bandwidth of 1 MHz and detection sensitivity of 1 nA. We chose AD811 and AD8615 as the main operational amplifier chips for the trans-impedance amplifier and also designed a three level enlarged circuit using trans-impedance amplification principle for the AD8615 preamplifier circuit. We also selected high-precision metal foil resistors with high stability as feedback resistor so that the entire amplifier noise was as low as possible. The second and third enlarged circuit with the AD811, for continuous voltage amplification, improving of input impedance and lowering of output impedance for the object, was achieved by circuit designing and making of the trans-impedance amplifier, to improve the loading capacity. The characteristics for this trans-impedance amplifier include; low cost and excellent performance, which provide broader prospects for weak signal detection in biomedical research.