A low-noise preamplifier applied to the intraocular pressure signal-detection system with 180 nm CMOS process was proposed.The amplifier adopts a diode-connected MOS transistor to achieve a large resistance of GΩ level.In the feedback loop,the pseudo-resistor and the feedback capacitor are connected in parallel to generate a high-pass cutoff point in the low frequency,which can suppress the DC-offset voltage and the noise in low frequency to achieve better noise performance.The post-simulation results show that the low noise preamplifier has a DC-gain of 40 dB,the effective bandwidth is from 0.25 Hz to 46 kHz,and an equivalent input noise is 197.3 nVrms at 100 Hz.The power consumption of the core circuit is 32.4 μW at a supply of 1.8 V,and the chip area is 0.75 mm×0.62 mm.