Abstract: To meet the readout requirements of high counting rate, large dynamic range, and low power consumption for Time Projection Chamber(TPC) detectors in high-intensity environments, a preamplifier chip with automatic gain adjustment was designed based on a 180 nm CMOS process. The chip consists of a Charge Sensitive Amplifier(CSA), a Class AB output buffer stage, a gain control module, and a trigger control module. Through on-chip logic signals controlling the switching of multiple switches, the chip’s conversion gain adapts to the input charge level. Additionally, switch bleeding enables the chip to operate at a counting rate of 1 MHz. Post-layout simulations show that the chip achieves an integral nonlinearity better than 0.4% across an input signal range of 2.2 to 16.5 pC. The chip has been submitted for foundry fabrication.