Aiming at the characteristics of weak photo-current signal and large variation range of photodetector, an all new structure of transimpedance amplifier (TIA) for detecting photo-current signal is designed in this paper. The detection current signal ranges from 1.6 μA to 1.6 mA, and the dynamic current detection ranges is up to 60 dB. The design principle of this circuit structure is to process the small current section (1.6~50 μA) and the large current section (50 μA~1.6 mA) for the photocurrent respectively by designing two TIA with adjustable gain and different gain sections in the circuit, and the gain is adjustable from 56 dBΩ to 96 dBΩ. Through the external output voltage saturation detection signal, we can select the desired TIA and its gain section. The PDK fabricated by 0.18 μm standard CMOS process is used for the circuit design, layout design and simulation verification. The test results show that the output voltage is 95 mV at the current of 1.6 μA and the output voltage is 915 mV at the current of 1.6 mA, which are in accordance with the simulation results. The transient characteristic of the circuit is good, the rise time is 5~10 ns, and the static power consumption is 1~2 mW at the voltage of 3.3 V. The indexes meet the design requirements.